It's not hard to apply a 10 minutes cooldown before any rested EXP starts to be earned... Actually that's how it works on XIV. You only start accumulating rested EXP after staying for a little while in your room, it doesn't come straight away.
So if someone would be crafting in his room, he would have to wait ~10min+ between each attempt in order to receive rested EXP. Which makes it impossible to really exploit.