My woodcrafter alt is level 8 and my clothier alt is level 10. Both are rank 50 in their respective crafts and make gear for my VR 12 toon. So, to answer the original question, yes. You can easily level up crafting only alts... just give them stuff to decon that your main toon finds.
dancing.in.the.webeb17_ESO wrote: »and by the way it's enought to have 40 lev in craft to make any vr12 items and have all usefull perks.