I don't agree with your stance on Big Team Halo being the ultimate for competitive Halo, but I see where you are coming from.
H2A is too easy and boring, it's better than Halo Reach, H4, and will be better than Halo 3 when it gets some maps. But, the core gameplay and playmaking abilities of individual players is too low for it to be truly amazing as a spectator sport. Halo 2 Classic and Halo CE are far better in this case.
In my opinion, 6v6 Objective based, Counter-Strike Style Shadowrun would be the absolute best Console Shooter eSport. Tons of strategy, improvisation, fun for spectators, longer kill times and engagements, and a nearly infinite metagame.
BTB Halo has some potential, but organizing it on LAN, along with making it better than a game like Battlefield seems improbable. Halo is a medium paced Quake game for Consoles, it should strive to perfect that niche.