Another thing that could be cool is a private rp rating, that gives you a certain amount of exp. per ingame hour, and is set by the GMs when they see you rping well, or decently, and can fluctuate between being high and low (depending on quality of rp--you get less for mindlessly grinding, and more if you're rping beyond a certain level, at the GM's digression within a set group of guidelines).
You have to realize just how much grief the GM team will get if people see them judging roleplay and trying to figure out who is doing a good job. There will be cries of abuse, favoritism, and how no GM is ever on during some person's timezone so they never get the benefit of this system. It's going to be pure madness.
On enforcing roleplay, I'm strongly against this, as are many other developers. We encourage, not enforce here. Enforcing may mean driving away people with potential who are not ready or willing to roleplay just yet. Many people with whom you have enjoyed great roleplays with did not start out as they are now, and they may not be here at all if they were greeted in the beginning by a GM waving a banstick.
The thing is: in the beginning, sure, there would be complaints. Favoritism, abuse, no GMs online, etc. Pure madness, perhaps, in the beginning. People will be mad that they aren't getting what they feel they deserve. Etc. People will leave, it wouldn't be a pretty sight.
However, in the place I brought this idea from (yes, my ideas aren't original. Oh noes. Our GMs are actually DMs), the general consensus (it had been in place for years by this point) was "if no DMs are online when you are, ever, suck it up", along with "abuse will be looked into, but not openly discussed"--the same for favoritism. Frankly, I feel sorry for the people on at 5:00 EST and no other times, because the chances of a DM seeing their rp is low.
I have a rather bleak outlook on rp in Planeshift if things continue as they are:
If you merely say "we encourage roleplay", you won't be doing anything more then saying "oh, roleplay is okay, if you want to do it, but hey, if you godmod/metagame ("my guildmate is now in trouble, a city away, I must be off"), that's fine too". Godmodding and metagaming are a lot easier then rping, and if allowed, many will do those (driving good rp'ers away from the game). Enforcing exceptionally strictly is bad (the ban stick should be used after repeated warnings over a long timespan, not before)--however, without enforcement, there will be about as much good rp as there is in WoW rp servers (from what I hear of them), except less so, because there isn't an rp planeshift server and a pvp planeshift server--all players of Planeshift will come to the same world. I didn't start out as a great rp'er either (I had come from playing Grindscape, it was to be expected. Either way, when I came, I had little knowledge of it, although I read the rules and tried it. I slowly got better. Those who cannot or will not rp, in my opinion, are detrimental to roleplay, and therefore, in the encouragement of roleplay, enforcement is necessary.), but from my time spent in Arelith (Neverwinter nights persistent world, they enforce rp with a rating, make it hard to grind, and in extreme cases they use the ban stick, however, the fact that it's harder to grind to get exp, and nearly impossible to grind to get money (daily crafting quota) drives away those who would rather grind then roleplay--enforcement of obvious metagaming/godmodding (using OOC information ICly) abuses, and such with detriments to the character (stat lowering), and in excessive amounts, the ban stick, keeps those who would do such things away or from doing them). I realized that while I was a relatively good rp'er here (from personal observataion; those who knew Garon's circumstances perhaps could speak better or worse of his RP, if not particularly well known--Garon didn't want to be well known, though, so it was IC to stick to the shadows, make few friends outside a select group), there I was average, at best, because the average was much higher then it is here, and still is.
In closing, the quality of rp is going to go downhill as the game gains more features, unless it's enforced, or given heavy shoves towards rp. This is because, as the game gains features, it becomes more likable for people who -enjoy- grinding and don't care at all for rp--and then less likable for those who enjoy rp, because it's disruptive to see someone chatting about game mechanics or the like.
Edit: In what way will rp be required to do things in the final (aside from NPC interaction, but that's always roleplayed to some degree, even in Runescape)? If not through heavy encouragement/making it seem better to the player xp wise, then what? This seems much easier said then done at this point.
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Also, a good policy as far as complaints about abuse/favoritism/not on at the right time in relation to the RP rating (or GM actions in general--it seems like a good policy to keep GM abuse reports private, if only because if the GM -is- abusive, imagine what they would do to someone who pointed it out on the forums?

) could be that reports will be checked out, but absolutely will not be discussed openly. Also, if there are 10 or so GMs who are known to be trustworthy (basically, a small, core group--from what I've seen, there is, although you never know), there would be a system of checks and balances in place that would prevent rampant abuse. Also, forcing them to give a reason (this would help the players, as well--for instance "very nice dialogue about the nature of government", or "how did you know your friend on the other side of the map was in trouble?"), and then checking that with the logs if necessary to see if they matched, would work as far as enforcement checkings.
Here is an odd thought (probably divorced from reality): make "City Guard" one of the preset classes distinct from the others in that it comes with specific stats, advances in a different manner no pps, no skill training and give it a non-lethal combat attack ability that bypasses the /challenge system. Thus players could choose to have one, not more, of their characters on an account be a city guard. Then when some players decide to start trouble in the plaza, say, one or more other players could log in with their guards and react. Obviously the idea needs more polish and the possibility of guard on guard action must be considered but there it is in a nutshell.
The result of the nonlethal combat would be to beat down stamina to zero at which point the luckless miscreant having failed to escape is knocked unconscious for an arbitrary period of time. Make it so that the guards cannot use their abilities outside of their spawn town so the wrongdoers can always escape to the wilderness if they are lucky.
Probably not something possible but something to think about anyway.
An interesting idea, although preventing abuse of it by players would be hard. Perhaps something you have to apply for the ability to do, or the like. City guards don't make for bad rp.