I've never used Sub::Compose in production, but you said that you're doing this for debugging purposes, so is that really a concern?

Not me ;-). The debugging statment was preceeded by "for instance". I don't think debugging is the only use for such a thing.

lodin complained about subtle bugs in various Hook:: modules, so I guess it's important for him not to introduce these by using "clever" modules.

As for Class::MOP, methods are subroutines.

Yes, but not all subroutines are methods. They follow a different dispatch (sub dispatch just looks into a single namespace, methods take @ISA into account).

So I don't see why something that is written for method dispatch should have to work for sub dispatch as well.

Does it really matter how it gets done?

Not if it actually works, and I don't have to learn about MOP to use it.