Please, please no experience or "leveling" by crafting. The last thing this world needs is more games with grinding. Grinding is the bane of all that is good in life.
Why would there be "grinding"? A lot of us enjoy crafting, but we also enjoy the benefits of crafting. Right now it's pretty meaningless.
Example: I have not yet played an RPG with crafting, that my wife has not enjoyed. Yesterday she said, that crafting is pointless and cumbersome. And I have to agree with her.

The benefits of crafting are minimal here.