In the same way you have Bounty offices where players can put a price on the head of another player in their PK range, and thus have an assassins anonymously murder the target and earn the copper for it, it might be interesting to expand the excisting mercenary guilds to include Player Characters among their ranks.

Now, this can take many forms indeed and it would open up quite a few new roleplaying possibilities imo, and mostly for the Warrior and thief classes. Should a player's role include or even focus upon it, they could go enlist themselves in a mercenary guild and offer themselves for hire to other players or maybe even cabals. They could serve as bodyguards or escorts (warriors), spies (thiefs) or soldiers or, well, whatever really. All the kind of stuff mercenaries irl do. What it would come down to is that they could announce to other players that their sword and/or skill is for hire for a price (which would be done in a similar way bounties are placed), and then they could go about their usual bussiness (ranking/pk'ing/whatever) until someone comes to the mercenary guild, reads the available info and the price of the enlisted mercenary player, and then contacts him to strike a deal and an agreement on the length, nature and duration of the service to be provided.

That someone could be anything from a lowbie mage that is looking for a high-ranking warrior to rank up through his painful levels quickly, (and of course, the higher the rank of the mercenary the more he can charge for his services), or even Cabals that can use these players to do their dirtywork for them without the enemy cabal really knowing that they were behind it, or to have the mercenary act as a spy.

Etc. The possibilities are quite numerous I think, and it shouldn't be all that hard to code. ...right?

Anyway, flame away.