...Every edges are filleted

Yes, in the real world every sharp edge needs at least a small fillet (unless you're making knife blades).

An automatic solution would be nice. I've experienced the slow-down and large file size increase after adding fillets, even in my moderate size models.

Auto-fit fillet would also be nice. That is, if two surfaces meet in a sharp inside corner and a large fillet is specified, the fillet could auto-taper as needed to meet in the corner.

Ed