I think with a bit more work, the rampage SD that's on Dretch Storm's server could be very good. For those who haven't played it, aliens are given 9 evos and humans are given a battlesuit, pulse rifle, helmet, and health regeneration, and all structures except reactor and overmind are destroyed (including spawns). It is still lacking in some ways (e.g. aliens can evolve to any class they want, but humans are limited to suit/pulse rifle), but it's a very fun end to a game.
I remember awhile back someone suggested that spawn times slowly increase throughout sudden death, like each time someone dies the spawn time increases by a few seconds, until not enough humans or aliens can spawn to defend their base. You can rebuild, but eventually you'd have to devote too many build points to telenodes/eggs.
The halving BPs is a cool idea as well, though eggspam is still viable for aliens on maps like arachnid, karith, transit, etc. Maybe you could allow rebuilding of all structures except spawns?