Thank you for all of your help. I recognize that I deny some advice that could help me lot in his response, but that's just where I'm a bit less competitive, and favor more personal preference.
I think I'll get rid of Aggronite for Aggron, and rather use my mega evolution on Latios, Blastoise, or preferably Nidoking when he gets his.
As for Avulugg, I was initially drawn back by his extremely unbalanced stats and poor type effectiveness, but I personally like the pokemon far too much to get rid of him.
Out of the pokemon you'd suggested, I think I may at some point invest in a powerful Zygarde.
As for Ferrothorn, you're certainly right about a defensive spread for him, and I'm going to change it to that.
Although, I think a Big Root would aid him far greater than Leftovers seeing as it would boost the amount of health he gains each turn, and the amount of health taken away from his enemy. I also plan on giving Leftovers to other Pokemon, and am going to follow the Smogon guideline of only having one of an item on my team.
I also prefer more reliable moves (Such as Seed Bomb vs Power Whip and Iron Head vs Gyro Ball) which are already quite powerful. As for a Relaxed nature, although it would help with using Gyro Ball, I will not be, and would prefer Careful or Impish, as they decrease SpAttack, a stat I'd never use either way.
And again, I really can't stand using moves such as Draco Meteor, which are less reliable and weaken your pokemon after use, despite how much better they could be.
With Psyshock however, I see how that could be very useful when going up against someone with high SpDefense, and I'll use that rather than Psychic.
I had found Ice Beam and Shadow Ball to help Latios more in covering various type effectiveness compared to the rest of my team than Thunderbolt and Surf (Although it was a difficult decision).
I'd never really understood HidenPowers -- they'd always seemed like a pretty weak attack to me, and it would probably be extremely difficult getting a Latios with a specific one seeing as they cannot breed.
I'm not much a fan of Trick or Defog, and I feel like Latios's lower HP and Defense would lead to him being a powerful first striker, in which he would win battles until they had type effectivness to take him down fairly quickly, making moves like Recover an Roost less useful.
You're right about Sheer Force being a much better ability than Poison Point -- I just hadn't like the idea of him losing secondary effects, but those would be less useful to him as a strong attacker (With poisoning virtually useless anyway, at this level).
And with making Nidoking a Special Attacker, it just always seemed so odd to me since he seems like a more physical pokemon, but I guess I'd already done so for the most part anyway. Your moveset does seem much better (Although an Ice Beam I think would be less useful than a Shadow Ball, as many of my other team members have Ice moves).
And I think a Life Orb would work quite well with him.
And yeah, Nidoking is completely outclassed by Incarnate Landorus, but there's no way I'd ever use one of them, as it's just so ugly and Nidoking looks so great.
As for Sylveon and Clefable, I could also never use them due to personal preference strongly against them. If I do not end up using Blastoise as my Mega Evolution, I will probably replace him later on. I'm mainly keeping him around for sentimental value as my first starter, and for type differentiation.
Thanks again for all of your help.
Ferrothorn would rather go Relaxed if you opt for Gyro Ball. Impish is fine if you don't use Gyro Ball. Ferrothorn is bulky enough to afford the 15% chance of Power Whip missing. It's the preferred option because of its 120 power being more powerful than 80. You do lose out on some power against some notable targets if you opt for Seed Bomb or Iron Head. If you want a Steel STAB, Gyro Ball is always the preferred option because Ferrothorn is so slow that it tends to hit its maximum power of 150 against very fast targets:
Mega Tyranitar:
0 Atk Ferrothorn Power Whip vs. 0 HP / 4 Def Mega Tyranitar: 174-206 (51 - 60.4%) -- guaranteed 2HKO
0 Atk Ferrothorn Seed Bomb vs. 0 HP / 4 Def Mega Tyranitar: 116-138 (34 - 40.4%) -- guaranteed 3HKO
0 Atk Ferrothorn Gyro Ball (150 BP) vs. 0 HP / 4 Def Mega Tyranitar: 216-254 (63.3 - 74.4%) -- guaranteed 2HKO
0 Atk Ferrothorn Iron Head vs. 0 HP / 4 Def Mega Tyranitar: 116-138 (34 - 40.4%) -- guaranteed 3HKO
Mega Tyranitar is fairly bulky on its own, but Power Whip and Gyro Ball make significant dents on it, which Seed Bomb and Iron Head can't accomplish.
Quagsire:
0 Atk Ferrothorn Seed Bomb vs. 252 HP / 252+ Def Quagsire: 268-316 (68 - 80.2%) -- guaranteed 2HKO after Leftovers recovery
0 Atk Ferrothorn Power Whip vs. 252 HP / 252+ Def Quagsire: 396-468 (100.5 - 118.7%) -- guaranteed OHKO
Power Whip OHKOs Quagsire outright no matter what, but Seed Bomb only 2HKOs it, assuming no prior damage.
Garchomp:
0 Atk Ferrothorn Gyro Ball (150 BP) vs. 4 HP / 0 Def Garchomp: 160-189 (44.6 - 52.7%) -- 23% chance to 2HKO
0 Atk Ferrothorn Power Whip vs. 4 HP / 0 Def Garchomp: 127-151 (35.4 - 42.1%) -- guaranteed 3HKO
0 Atk Ferrothorn Seed Bomb/Iron Head vs. 4 HP / 0 Def Garchomp: 85-102 (23.7 - 28.4%) -- 94.4% chance to 4HKO
Seed Bomb and Iron Head are pathetically weak compared to Gyro Ball and Power Whip when they hit Garchomp.
Aggron's viability all stems from its Mega Evolution. Not using it is a no-no. Vanilla Aggron's defensive typing is outright terrible; it's weak to common types in Water, Ground and Fighting. The latter two hurt really badly, as they're 4x strong against Aggron. Not even 180 Defense can save it.
Leftovers is always the superior healing option on walls, including Ferrothorn. Big Root is just a waste of an item slot, as it only works on draining moves. Ferrothorn won't always have time to Leech Seed an opponent, or it may be up against a Grass Pokemon, or a Magic Guard Pokemon (both of these kinds of Pokemon Pokemon are immune to Leech Seed). It's always nice to have a source of passive recovery when you can't Leech Seed something; therefore, Lefties > Big Root.
Some Pokemon are meant to be hit-and-run attackers, which Latios is. It gets in, Draco Meteors for massive damage and gets out. That's very true for the Choice Scarf set, as being locked into a move may be disadvantageous. Ice Beam is redundant with Latios' Dragon STAB. Ice and Dragon shouldn't be used together, really, as both hit Dragons for supereffective damage. You'll always want to go with the type that gives STAB; in that case, use Draco Meteor. Defog is a great move this generation; it clears away entry hazards from both sides of the field. It's useful if you hate Stealth Rock, Spikes, Toxic Spikes and Sticky Web with a passion. Latios is supposed to use Defog on any switches it forces, which it can do rather well. Remember that Stealth Rock is a very popular move, and removal of the hazard from your side of the field is incredibly helpful. However, you have to be careful when using Defog because Bisharp can switch in and gain an Attack boost with Defiant when its evasiveness drops. Recover or Roost give Latios more survivability, despite its frailty on the physical end, so that it can keep coming in and out of battle to dish out as much damage as it can. Trick in conjunction with a Choice item is meant to cripple walls that are dependent on their items, like Chansey. If a wall is locked into a single move by a Choice item, its effectiveness is severely hampered because it can't switch moves. As for Hidden Power, it's a nice bonus for Latios to have to hit specific targets; without HP Fire, Ferrothorn walls it completely. Hitting Scizor without resorting to Surf or Thunderbolt is also a nice bonus.
As I mentioned before, don't use Avalugg. Its bad defensive typing hinders its walling capabilities if you didn't get it before. It's also very specially frail, even with significant investment.
Shadow Ball doesn't do much for Nidoking, really. It only hits Ghosts and Psychics, which are already taken care of by Earth Power, Sludge Wave and Megahorn. If your other Ice users are down, it's always nice to have a backup Ice coverage move on Nidoking as a failsafe.
If you keep Blastoise, you'll have to take Aggron out of the team, as its Mega Evolution is the sole reason why it's even used in the first place. And Blastoise should look something like this, as its current EV spread lacks power:
-Water Pulse/Scald/Hydro Pump
-Dark Pulse
-Aura Sphere/Ice Beam
-Rapid Spin
Nature: Modest
EVs: 252 HP/252 SAtk/4 SDef
Item: Blastoisinite
Rapid Spin is also a staple move in standard play, as it's an alternative method for clearing away entry hazards. However, Ghost Pokemon block Rapid Spin from its hazard-clearing job, which is where Dark Pulse comes into play: Mega Blastoise can blast away incoming Ghost Pokemon eager to block Rapid Spin with Dark Pulse so that it has more opportunities to Rapid Spin away those hazards.
Edit: not everyone plays with item clause (when all Pokemon on the team must hold different items) because multiple Pokemon on the team may need Leftovers or Life Orb to function at their best.