The constitution states that every char has to be able to craft and fight and that's that. If constitution says that, then the 2 default necessities are crafting and fighting regardless what players expect. So in the end they get to choose 2 things: how they fight and what's their profesion.
But characters "all-in-one" is really bad idea...
Alts is always a problem. This doesn't have much do with this specific mechanic. I'd say just about any feature is affected by it.