I'll come back to the original post, because I read too many digressions here; the thread being combining RP and PL, and not comparing IC and OOC. For that matter, I'll personally use RP and IC as synonyms.
Therefore, I understand the question as "How can we RP when leveling, and level when RPing?". Because you don't marry people by force (anymore), that would be the way to make 2 arguably opposite kinds of players interact. Well, first, same method for both: show them that combining is just more fun. RP your training/practice routine and it will be less of a routine, and RP your actual character, otherwise just call it storytelling.
For example, play a clumsy hopeless thief if you want to be a thief but don't get any better at it. Rob, fail, run and get mobbed and stoned or lynched everyday. Become a famous loser. And don't forget to die often. That's the point of RPing; it's not about showing off, it's about being someone you won't be in real life.
I think the tools for RPers are more accessible. Inconsistencies are only there because the game is far from complete, and players know that. One day, would-be wizards won't need to go mining anymore.
For PLers, the opportunities of RPing are a bit more scarce, or at least not that obvious to the players.
- The first opportunity to RP for a PLer is the economy. As I see it more and more player controlled, that's the way to go. Now, trading in itself is no more role-playing than socialising. How to stop all the disguised PLing that is the current market, I don't know, but I hope the Auction tab will disappear when in-game substitutes will be there (like fixed billboards, payed selling stands and taxes, illegal hawking, or whatever is planned).
- The 2nd best opportunity is player-to-player teaching. The subject is already debated elsewhere. But if no RPer levels up, that feature would be useless.
- Events are great for that purpose. Maybe GMs will design events for more PL-oriented players, meaning: where these players tend to be more often, like the arena. There would be RPing PLers anyway, to contaminate the PLers who don't really know what a role is.
- Player events would do the same. Sfmluth the wizard goes to the arena to recruit 1 or 2 bodyguards for a trip, so sets up an instant mini-tournament. Of course the competitors have to speak and RP to be chosen, for they need to be reliable. Benefit for the kid whose Doom2 teleporter accidentally brought to PS? Something valuable given by Sfmluth, and an introduction to a possible different way of playing. Benefit for Sfmluth? None, but he is a hardcore RPer, a missionary, so his suffering and expenses are worth it.
- I've never dueled, but I think this doesn't exist: when a challenge is accepted, have an open verbal phase. It can be used for prestige, taunting, whatever. PLers would surely do something with it if it can bring them some benefit for the physical contest. Along the same line, have a verbal phase when one fighter is dead, for last words, curses, final humiliation or whatever. The point is, a good RPed actual fight is more fun than a dice controlled silent fight or a RPed blah blah resolved fake fight (which is not, actually, RP).
- Can you actually run away from a duel, and get out of the challenge mode? Retreat? If not, I see that as necessary. As well as a "surrender" command. Penalties satisfy the PLer, while the RPer has more choices for his acting.
- Quests are actually an intermediate to role-play. Some quests should be famous for requiring some fighting and good reward. So famous that no new player can ignore them for more than a few hours of play. NPCs mention them, like the combat trainer when he is not even asked. Signs mention them. Players mention them openly, for they are told to spread the word. And they tell you who to go to to get the quest started. Of course, the fight part is the core, but there has to be some chat with several NPCs as well.
I know that I concentrated my attention on the fighters, but that's how I understood the post. Rising ones craft is not PLing, it's IC. Mining to become a fighter is only temporary, not a game feature.
It's good to have all sorts of players around. Doom players can't bother me, because they can't force me to fight. They may, but only if they RP first

. I find a lot of features in the game OOC, on the other hand, but I care little about it. Hydlaa is full of people, you can meet many, and many you won't talk to again. That's IC as well. It's not up to role-players to attract levelers, it's up to the game, and to players who explore all its aspects, to attract all those who don't know all the possibilities. Attract with honey. Hell, play it right, and I may even duel some day.