I'm not even sure lowering the housing needs would help that much: Gestalt Empires are awefull at providing amenities / maintenance and also suck at crime-fighting. Both aren't large problems on lightly populated worlds (since then replicators are comparatively strong and the capital pushes you into the positive for both resources), but they become very visible at around 100 pops - this is the point where you have to sacrifice 2-3 building slots for maintenance and another 1-2 for Sentinel Posts.
And since both Nexus Districts as well as Maintenance Depots provide both housing and amenities you basically don't get one without the other. My point is, there isn't much reason in giving MIs tons of free housing if actually using the housing means going into the red for amenities - which you can't fix without ALSO increasing your housing at which point you have only really prolonged the problem.
Furthermore, as much as I want machines to be stronger and potentially also more unique (as in, not just having the HM advantages and downsides), I don't think arguing from a realism point of view is of much use - clearly, Stellaris is not that realistic and in reality any GC would probably just run over every regular empire. Logically, they would have absurd growth rates, insane efficiency, no internal problems and since Stellaris' GCs clearly are able to produce somewhat self-aware beings (Leader drones) they could also do a constant, yet controlled, wargaming secession against themselves and thus also you creativity and unconventional solutions, i.e. literally the only advantage regular empires would have. Balance wise GCs (and especially MIs, since they don't even have any biological restrictions) should be completely overpowered. And I definitely don't think that this should (and will ever) be the goal - outside of mods.
I do, however, think, that MIs need a buff and since efficiency just sounds like a very fitting focus for an unemotional superintelligence, actually doing the things that were planned for MIs in the DevDiary might be a very good start. Furthermore, machines just need some equivalents for features of biological empires - they are lacking out on so much stuff others have it's not even fun (LG ascension perks / paths, advanced traits, numerous edicts and decisions as well as certain events and anomalies).