It's up to you really. You'd probably want to go with Pokemon that can help support your other Pokemon, so for example if you were to go with Archeops and Thundurus you'd have an ice weakness, so you could use Volcarona with Quiver Dance and a strong special fire type attack as a switch in when people go for the assumption that you'd keep your other two in (actually, that's a lot of ice weaknesses, so best not to choose too many of those :x) Starmie could be useful for Tyranitar if whoever you faced someone who had a fighting type, then boom switch into Starmie and utilise its Psychic attacks.
Either way, moving this to in-game section for people to comment upon which Pokemon in general would work best with each other, but I'd probably go with those five and another if it were up to me. After you've made a decision, then it's best that you come up with a moveset yourself and everyone else can help you improve upon the movesets and then comment on items to be used, etc. :)
