Well, as long as everyone is able to collect resources to sell, markets will get cluttered and no-one will trade anymore.
I too see that problem. There definitely are some resources like cobble or planks which are over-abundand in the game. Everyone has them and everyone sees farming and selling them as an easy way to make money. Finding a spot to sell those resources for more than the iSell prices of the IronCity-market and buying other resources like diamonds and stuff for less than the iBuy prices WILL be nearly impossible. The huge difference between iSell and iBuy prices won't force ppl to trade those.
But there surely will also be resources like glass, sand, coal, iron, redstone, lapislazuli and dyes in general, wool, gravel, flint, feathers, arrows, and other resources which some players need and other players have. And the huge difference between iSell and iBuy prices will almost always make it attractive to trade those. (So the personal market chests selling/buying THOSE resources will indicate a working or failing of the markets.)
I meant more like disabling "useless" skills for different professions, like miner could only mine and dig, artisan could only cut wood and craft, etc.
Oh-h-h-h... I see. Actually, that is doable. each MCMMO skill can be enabled or disabled per-person so it could be down
Disabling skills isn't a good idea. If you like to mine your mining skill will quickly go up ayway, if you like to work with wood your woodcutting skill will rise faster, and so on. Additionally what would you do to ppl like me who like to cut their own wood, mine their own diamonds, and fend off mob intruders from their land all by themselves? Block all skills? That would be quite unfair for them. Allow all skills? That would be unfair towards specialized players. Force them to choose? I don't really think i could. And the chance is high that desired skills will frequently change.
Imho a good idea would be to create the possibility for players to ask a mod/op/howard to transfer experience from skills they don't need to skills they frequently use. So for example a miner can transfer all his EXP gained by dropping from cliffs and cutting wood to his mining and repair skills. There obvously should be a certain fee involved (10% ?) to prevent switching all your exp to the skill you want to use next. One problem might be that skills like acrobatics are definitely easier and quicker trainable than skills like taming. So it might be neccesary to weight the exp of certain skills differently (or just create a conversion table with the 10% fee already included).
The commands to take and give exp are already included in MCMMO iirc.
(Sorry for helping to turn this thread into a discussion about economy, but if you are forced to spend money for certain things (i'm still trying to gather enough for my residence protection) you have to make sure that you can gather money easy enough to not scare players away.)