1: as Ohirra elegantly pointed out, you need all three districts to get a full complement of buildings, which is extremely rare.
2. Those districts are weaker than normal districts until specialized. Normal mining districts give 200 miners and +100 on specialization, while Void Dwellers get 150 miners and +150 on specialization. To solve this, I recommend "functional architecture" civic or it's authority-dependant options.
3: for food-eaters, food is tied to energy districts outside of Hydroponic farms. This means it's difficult to specialize a habitat specifically for food to maximize efficiency without doing something pretty inefficient such as disabling technicians and just having 100 farmers per energy district. It also means energy and food are competing for the exact same slots in general. To solve this, I have found "Phototropic" to be an incredibly useful trait, but that restricts your species options to plantoids/fungaloids. Alternatively, you could voluntarily weaken yourself and go Lithoids.
4: Void Dwellers in particular I don't think actually get that much when compared to simply grabbing Voidborn mid-game. As far as I can tell, the only real advantage they get now is +15% Job efficiency on habitats and two mostly-useful tradition swaps. Though these come with the consequence of suffering on planets unless you get another species. The bonus starting tech is mostly to make playing this origin even viable and offset the starting weaknesses. Unironically I think the "strongest" effect is you save an ascension slot, which does feel a little...bland.
5: No advantage from Orbital Ring related bonuses. These can be quite huge. Noble Estates only give +100 Noble jobs, but the orbital ring version gives +200. Apparently Ringworlds "in general" get certain buffs to certain buildings to compensate for this, but I don't see habitats getting the same buffs.
6: New habitats cost alloys, require alloy upkeep, new districts cost more total in alloys than normal districts need minerals and also demand an alloy upkeep per district, it's just generally a lot of alloys. Considering that you have less maximum output potential than normal planets due to all of the above, and even have less per-pop efficiency, it means that you are kind of on the backfoot.
So Void Dwellers have some weaknesses compared to normal empires. The primary advantage seems to be +15% job efficiency, which IS pretty good. It does feel like it strongly promotes certain build choices, like Phototropic and Functional Architecture, at least to start.
Part of me is curious about bringing back "small habitats" from before they were consolidated into the one-per-system model we have now under the new economy system, since part of the issue that provoked the change has been fixed (pops don't cause lag anymore). However, since there's still no kind of auto-siege and auto-invade system, the other reason for the change hasn't been solved yet either.
My suggestions:
1. If a habitat is missing a district type, they instead get a habitation district slot. Much like ecu's, specializations on these secondary habitation districts should grant double the effects and jobs to compensate for only one zone slot. This way, they can get a full complament of building slots without losing district efficiency.
2. To assist the above, habitats will have decisions to replace resource districts with the above-mentioned "secondary habitation districts". This can help specialize a habitat a little bit further, and help solve weird edge cases where you intentionally want to dismantle habitation modules that grant an undesirable district.
3. Habitats will be able to have "Space Docks" built on them by construction ships. This is functionally their version of Orbital Rings, though perhaps replacing "habitation districts" with something more appropriate for habitats. I also think this system would be appropriate for Ringworlds.
4. A balance sweep should be conducted on planetary decisions and thematically apropriate versions should be made for habitats. Things that come to mind include resort, penal, and thrall designations, "Mastery of Nature" decision, and others.
5. It might be interesting to have some interactivity between habitats and starbases. An example that comes to mind is Hydroponic Bays could unlock dedicated Hydroponic Districts for habitats in the same system, or boost farmer output on habitats, or it's own food could scale with number of habitat farmers.
6. Specifically picking Void Dwellers feels like it should come with some more uniqueness compared to normal empires. While I respect that the habitat related stuff is mostly acquirable for normal empires so you don't have Subterranean's problem of "I conquered this planet and magically it's infrastructure is now insufficient due to lacking the correct origin", but I feel like more could be done to further incentivise actually picking this origin.
Another, very exotic approach is to ignore all of the above and move Void Dwellers from an origin to the "planet class selection" screen. This then allows Void Dwellers to have a much more impressive selection of builds, as it could be combined with things such as Machinist, Under One Rule, Overtuned, or just flavor options like Cybernetic Creed.
