It could be technical problems. I got one game with that kind clothes layer system, and it runs like... Well like shit. Name is Flash camping, it stutter a lot, same as latest version of Defenestration. You can check it out, not a bad game, but with technical problems. And yes, there is pretty complex system in that game. Layers, time tracking, weather system, maybe another thing. Can't remember. Have feeling unity engine would be better choice for project, just a hunch you know. Maybe there is way for solving issues, but could be engine just hit it's limits. Still I would not give any money if progress not made for so long.