Having to collect low level materials to make an item for an alt or a new craft is indeed a chore to me. Specially if it involves having to go to a specific place far away. It would be great to have your retainer handle that.

Maybe make it so they can gather stuff only 10 or so levels below your gathering level? And put a limit to the quantity you can get that way per day?

That way the only practical used would be to get a couple. items to craft something or to get the last few points of crafting exp in a level. But if you want stuff to make money or to really grind crafting, you have to do it yourself.

Thinking ahead, it would be cool to have smart phone apps to use them. Imagine sitting at work and thinking you wanna start an archer and would like a new bow, but your carpenter dies not have the wood. Use your phone to have your retainer gather it and when you get home, all you have to do is craft.