[..] enforcing consistent roleplay.
[..] roleplayers shouldn't be just favoured; they should be the only type of players.
While I pretty much agree with whats stated here, as well as with approving some guilds will at the same time give off-setting guilds a valid right to exist, we mustnt forget that Planeshift may, if at all, -encourage- roleplay, but no way wants to enforce it! As said often enough already, Planeshift is not a pure roleplaying game, its a game where mechanics-testers, roleplayers and levellers all do have equal rights, are they interested in setting and background stories, on exploring exploits and glitches or determining max stats and skill levels. The only official agreement seems to be "Try to avoid ooc talk in main". And even here theres no enforcement but still a more or less vague "try".
Right that lack of Planeshifts definition I see as a problem to set up something like this thread here is about.
If indeed roleplaying will remain 'unenforced' and just one more option among several ones, then I may tend to in fact split it as said initially: Out of all guilds, reward roleplay focused guild with something supporting their roleplay. Generally I would at least create 3 groups, "lawful", "outlaw" and something like "others" (dont discuss the naming, you get the picture). The whole concept though would have to be as flexible as possible, treating each guild and its idea individually, otherwise created guilds will tend to be all clones, trying to receive those 'rewards' or benefits.
The given rewards of course will have to be fitting the guilds purposes, rewarding a guard-like guild with magic wands because they are special and fancy would be pants (like dlayos dropping wooden staffs), rather rewarding them with common Enforcer Shields for instance would be like fitting.
If on the other hand Planeshift one day may be defined as a pure rpg, then all guilds will have to be conform to the setting, approving few only an absurd approach. Unless you would want to have few guilds to support the setting actively, like a guild "Sunshine Recruits" or "Black Sparks" (Flame..) for instance. But since at once many applications will pop up, more than one of them promising, it will only end up influenced by favoritism by the people in charge and cause trouble (nothing to complain about, but favoritism will always occur with people deciding, willingly or not).
However, Planeshift getting a precise and unambiguous definition to be an rpg I seriously doubt. So I cant see a way for both options: Certainly splitting guild-types into groups approved/not-approved will to be too much of a definition Planeshift being a Not-only-RPG.