Emerald Frontier Team

Hi, now i starting to play battle frontier.
Currently, I'm using my standard 3 and just gotten a silver shield in battle tower.

Swampert Relax nature @ leftover
surf
ice beam
protect
earthquake
252hp, 120Def, 136 att
(Physical tanker and help in clearing dragon-type)

Gardevoir Timid nature @ bright powder
Calm mind
phychics
thunderbolt
WoW
252spA, 252 Speed
(Spec sweeper+Spec wall)

Salamence Adament nature @ Choice band
Aerial ace
Earthquake
Rockslide
brick break
252att, 252 speed
(Physical sweeper)

I think/hope i can get gold shield in battle tower after i get choiceband and rockslide on salamence. I wonder what other pokemons can i add onto my team for battle frontiers without using any so-call allowed lengerdaries like regi's and latios/latias. And if possible, only include pokemon from emerald and not traded pokemons. I heard battle palace require some specific nature to be good in it, battle factory is about renting pokemon (so it is not about my pokemon team) What about other 'gym' in the frontiers. I hope i can get gold badge in all the gym in the frontier.

Any recommendations/suggestions on my teams will be much appreciated

I have never played the Emerald frontier, but so far your team looks very good. But I would suggest running Dragon Dance on Salamence (which will require breeding, sadly) Else it just lacks the power to break through some of the stronger walls.

Another suggestion is replacing gardevoir by this guy:
Metagross@Choice Band
Meteor Mash
Earthquake
Explosion
Sludge Bomb

And you could then add a Breloom, which covers the rest of the team:

Breloom@Leftovers
Spore
Substitute
Leech Seed
Focus Punch

OR

Breloom@Leftovers
Swords Dance
Sky Uppercut
Sludge Bomb (Or hidden power if you got a good one)
Spore