Idea that would be probably too complicated to implement:
On death, units (including engineers) are instantly transferred to ally. This incentivizes using your ACU in risky combat and investing in units. Direct resource buildings (mex, pgen, para) are transfered as well.
All other buildings become neutral and must be recaptured (somewhat easy because of transferred engies). Since the neutral base does not have resources, its shield and radar turn off. In addition, PD turns of until recaptured by any player (otherwise they would suddenly start shooting former allies. Alternative: PD just gets killed).
Basically killing a player would open up their entire base to easy damage (because no shields) until the allies of the dead player manage to recapture the structures, but eco ist not lost. At the same time enemy players can steal the base by capturing themselves, creating an additional strategic option. The player that received stuff will have a slight buildpower bottleneck he neads to deal with unless he was stalling a lot before.
And this means that killing a defending/turtling player is more rewarding than killing a spamming or pure ECOing player.
Imo the goal should be to hurt player deaths in lategame more than in early game, and should hurt people that are build power bottlenecked more than people who are eco bottlenecked.