Why not make ra/ex gear for your job class to help crafting, similar to ffxi (gear that gave +1 to skill, not stats; lvl 20 = lvl 21 with the GM body). I even like the idea of crystals or dyes being sold for GM that would 'sign' an item.

I always thought it was very cook my linkshell friends were running around with gear I made, with my name on it.

I really like the idea of turning in marks for exp. My level 42 alch for instance: trade 1000 marks for 100 exp. Sure would help during those tougher stages.