I've been calculating how many colliders it takes to make a decent sized house and have found out that it wouldn't take many to reach the collider limit in Unity. The upper limit is supposed to be 250k but its been found that reaching 150k has a huge performance hit and currently going higher then that is unwanted. These houses are also not static since they are built on the fly. That means no precompiled occlusion culling which results in a huge performance hit when 70+ are on screen. Dynamic occlusion culling could be a fix but the problem remains of hitting the collider limit. So, with that, i've scrapped that building feature for a more simplistic one.
The future building system will be use pre-made floor plans. You will place a foundation down and complete it's construction in steps showing progress about every 20%. Once its complete there will be a limit of about 50 objects that you can decorate your house with. This would support 1000 players having housing in an open world with room for everything else. To make up for not having complete customized housing i'll add in the ability to change wall/floor textures, doors/windows with housing addons later. This will still offer a good degree of customization with much better performance.
Current priority before this change was AI/combat but with the current hole in the feature list it's being diverted back to housing. One week should be enough time to complete the swap and old progress will resume.