i think you actually have really good idea here.. people automatically just poo-poo it without considering it.. i think it would work as long as the cost of the runes balanced the increased income from faster collecting... i think it's an excellent idea.
i have an idea, why not make it almost like the coal mines in P2P, so you'd give your loads of lobs or swords to the captain, and then pick them up in port sarim?
why not have an echanted amulet that helps with mining or smithing... maybe it would give +1 to each skill... the gem could possibly be a new one, only found when mining rune?