Not really necessary, but it would help a lot with some RP: Improve the chat window. Make it easier to write longer chat lines (Maybe multiline edit) and support copy and past from the chat history. Maybe customizable tab-completion not only for names but also for some often used words like Hydlaa or Yliakum (allow people to add their own words to the tab-completion).
Already suggested a few times, but I still like the idea: Add a specified /roll command for stats to support Role-plays that the mechanics doesn't cover (and maybe will never cover. I doubt there will be ever support for arm wrestling in game. But with both players doing a "/roll strength" and comparing the results this could be still possible with game mechanics involved somehow). I don't think it's a very good idea to limit RP only to what the game mechanics support. Role-playing is something very creative (The reason why I'm so bad in it

) and no game mechanics will ever be able to support everything. So I think it's better to give people some generic tools for certain RP situations that still allow them to involve game-mechanics in some way.
Not sure if possible with the current mechanics, but create a guild-message board with an un-takeable book for each guild (if the guild wants it) that the owner of the book can still edit. Just a place where all guild can announce their events without involving GMs each time and paying for the posters.
An improved /ignore command that allows you to only blank out what a certain player says in the main chat. Just a tool to stop ongoing RPs from being disturbed but that allows to clear the situation and talk to the player afterwards when there is some more time for this

. Yes, I know...I should try to get along with all players and their way of playing...but sometimes it's really too annoying to deal with a player immediately and stop the RP for this. So I think a Mainchat-ignore with a short message to the player that he is ignored will be helpful in this cases. And I for myself think I will have much more patience with other players when I can choose the time when dealing with them and don't have to stop the RP for this.
Remove number values like slash, speed or quality from items. Knowledge like inferior or finest steel stock should be enough and will force players to exchange much more knowledge about the different looted weapons to find out which weapon is better. And without these values the information exchange will be more IC too I think.
And now just some thought on the training system:
I like the possibility to change a chars profession after some time (or some RP events, like a injury or such). That's why I'm against a skill cap. The loosing levels idea when not using a skill seems to lead only to people spending much more timing training to keep their skills from decreasing. So not too sure if this would really support any RP. I prefer if each level you gain would increase the experience you need to gain any other level. (For example a plus of 10% on the needed practical experience for each skill after you gained a level in one skill. Would mean that a 150 Brown way mage needs 1500% more experience to for each other skill level

). And like already suggested thousands of time...remove the PPs. Make skill training only based on practical experience and make training with a NPC trainer take away some percentage of the needed practical experience to level up. (For example 25% for each training lesson with a NPC with a maximum of 3 training lessons with a NPC: example (PPs = training points needed, lack of a better expression) 100 PPs needed -> one time training 75 PPs needed -> second training 56 PPs neede -> third training 42 PPs needed). This way players could train even if they doesn't have a trainer (or access to one, like thieves who can't get in town

). And with proper prices players had to spend much less time in the mines and could spend their money for more important things..like beer

. And the prices NPCs pay for platinum and gold could be lowered drastically.
Last but not least I agree with all people who wished for more (RP) items and possibilities to earn money without mining or endless monster slaying. But the only addition I have there it that it would be nice if we could gain some items without questing for some days and then not finishing the quest just to get a skull or a whetstone.