This assumes your time isn't valuable, because swapping people out at the Hall every time you craft makes crafting even more of a tedium. If you want to save time, you don't segment things off like that. With +Crafting and +Blacksmithing items, the ability point investment is meager anyway (2 hard points in each for 6 ability points total, assuming Scientist talent; less if Pragmatic trait).
I just tried it, it takes less time to swap out to a fully crafting ready henchman and hand him the latest crafting supplies than it does to change into your crafting gear and be handed the latest crafting supplies.
