You answered the inverse to my question. I asked what would happen to the game play if rants were removed and chainsuits remained.
My idea is to have stage advancement based on the kills of the enemy team rather than your own team. Your team advances to the next stage when/if the enemy team gets X kills. This idea is based on how evolution and technological research occurs in real life. Things that don't do well prompts change, things that do well remain the same. This can be further enhanced by allowing the possibility of staging down, and even making the staging nonlinear but rather structured like a tree. You still get rewarded evos/credits the same way as before (essentially) so there still would be a direct reward for doing well. But again, a game play that has a feature like this, would not be considered 1.1 vanilla game play .
I've seen that feature in action before, I'm not a huge fan of it. But also, how does that encourage more forwarding before sd rather than just making a stronger main bases? DevHC brought up a good point:
Gpp vanilla implemented a version of this with zoned bp based on the power ranges of repeaters, but as I've said, that implementation had many problems.
But also the actual difficulty for humans to build forwards needs to be considered. A ckit needs to be escorted by one or more combat teammates (unless the ckit gets really lucky wondering out on its own). For a fully functional basic forward the ckit needs to build a repeater, a telenode, an armory, and a medistation. each of those buildables can only be built by the ckit one at a time, each takes time to construct, and the ckit can't get a combat weapon (if you don't count the blaster) while buildables are constructing so the escorting combat teammate(s) need to remain at that location to defend at the same time (assuming the ckit isn't "speed building" and that requires a telenode and timing to make sure the ckit doesn't respawn at a different location). This is not counting any defensive buildables.
For aliens to make a forward, a granger (while not being effective in most combat situations, its mobility allows it to avoid encountering combat humans pretty well, and sneak around a map pretty quickly) just needs to build one egg, and the aliens have all they need for a fully functional basic forward, and anything else would be a bonus.