...what would be your dreamteam?

I don't know what is the optimal teamsize for competitive Attack & Defend, since there is no such thing, but let's run with 4 now.

What are those abilities that can be used in A&D, and if there was a $100,000 A&D LAN tomorrow what lineup could possibly rise to the top?

My dreamteam would be:
Italy stermy
Italy H41
France winz
France aKm

I personally had the chance to play against aKm back in a while in the A&D sampler on Courtyard. He totally crushed everyone, and H41's CA experience would come in handy in the CA-style CTF gametype. I generally think stermy and winz would be top players in anything they invested time in.

Moreover, the team cohesion would be outstanding. stermy and H41 are brothers, winz and aKm are brothers. Stermy, winz and aKm play together in one team in Shootmania.

Is there any lineup that could stop them?