WTF are you talking about? What is a “proper” piston?
You can stack gaskets if you change blocks. This **** isn’t as hard as you want it to be.
It doesn’t limit anything unless you limit it.
How many times have you checked p/v clearance with an off the shelf piston?
Do you know how much that clearance you actually need and why more clearance is bad? And why?
It’s for the same reason you see some unlimited class stuff with very wide LSA’s. They don’t do that because the wide LSA makes more power because it doesn’t.