I don't mind the regenerating walls, but it does seem silly that they regenerate without having to put any additional resources into them.
It would be cool if the cupboard had storage slots that you could load up with wood, stone, and metal frags that would server as the reserve for regeneration. Then once those are depleted, regen would stop until the cupboard was refilled.
I really love this idea, It would also work with decay,.. the walls decay and automatically repair from your cupboard "stockpile". But once the cupboard runs out of material/supplies. then the house starts to decay naturally.
So not only will old unused houses decay, but you can't also fill up your cupboard and not log in for a day or tthree without worrying that your base will be decayed and gone.