Fantasyfiend has mentioned many of these points (great idea by the way - keep it up), but I think he has a good idea with the Jester class.
I was planning on forming a Jesters guild myself (in name only). I was also thinking to recommend adding Jester hats to the wish list. And then I saw this thread...
I think that the humourous spells thing is ok if implemented with restrictions, and the idea of a bard class, and in particular the Jester class is a great one.
Jester could be a subclass of Bard. The Jester could have a high luck rating (for defence but not offence), and spells (with high chance of success), but be a below average fighter and not good at crafts. Basically a very niche group. There could also be Jester hats & clothes which could only be worn by Jesters. Additionally the Jester clothes could only be purchased in specific places and would be expensive and a great matter of pride to the class.
I think that Jesters would have to be of good or neutral alignment. If they became evil then their spells would take on a more malicious form and they would change to an evil bard & it would take something very hard for them to change back to a Jester (not just alignment - maybe their Karma could shift towards evil at 2x the rate of other classes; making it a challenge to stay part of the subclass). Even in neutral alignment their spells would be weakened.
There would have to be very few incentives for a person to become a Jester besides entertaining people (low levelling speed, etc) which would weed it down to the few who actually had intentions of role playing the class.
The extremely high level Jesters could be given the title Court Jester. And could be entertainers and possibly advisors/spies for the most powerful Guild Leaders.
The Jesters could have two types of tricks (spells):
1. Ones for combat (which would mainly be defensive/illusion type and only available at higher levels)
2. Ones purely for entertainment. To help prevent Jesters being a nuisance the entertaining tricks could only be of these types:
a.) Trick type actions. The Jester Juggles balls, walks on his/her hands (PS how sexy would a female Jester look LOL

), does a backflip, or does a dance. These could be class specific motions like the regular \'sit on the ground\', or \'nod head\', \'act drunk\' ones\' normally used to spice up chatting, but in this case used for being a public spectacle!
b.) Self inflicted spells lasting for brief periods of time.
Eg: Jester turns himself into a pig. The pig is talking to people! - Funny AND it hasnt ruined anyone elses gameplay. The Jester is almost like a NPC in this way!
c.) Spells that affect other people (only available at high levels), but are easily removed as soon as the PC leaves the vicinity of the Jester. It wears off when they are not near the caster, and they can get on with their quest etc.
There could be some coding to make it that the more people that are within the immediate vicinity of the Jester, that their trick spell mana is heightened, so that they can perform for longer. Kind of like drawing off the positive energy of others (but not literally!). This would mean that Jesters who were actually FUNNY and could keep a crowd, would be able to do their acts for longer.
From lvl 0 character, you would have to reach a certain level before you were even able to perform tricks (spells). This would ensure that only people who wanted to be Jesters and not just rogue type bards would stay with the sub-class.
The Jester could be like the bard and have an instrument (lute etc...) for playing tunes. and when they are in a group (and within the immediate vicinity) they increase the strength of the other members but not their own. This would enable them to travel to their next town (gig) as an asset to the group, but they wouldnt really be suited to questing due to their combat weaknesses.
The very last thing is that the Jester can run fast. And is agile at avoiding flung tomatos... LOL. Being able to run fast helps to add to their mischievous (but not aggressive) character type who will live to joke another day.
Additionally there could be a Jester guild. This would keep the Jesters/Bards together to amuse themselves in times where the public did not welcome their antics. It would also encourage the forming of small groups of Jesters performing as a travelling act. Perhaps busking for money or playing for hire at inns (to attract customers) and castles.
Including the Jester subclass (read class, if the Bard class isnt implemented) would be more in keeping with the fantasy genre as well - cities were a place where the lower classes welcomed public debate and shows to keep their low spirits up.
Some people have been mentioning making PS an original game by giving it things other mmorpgs dont have. Well the Jester class is still up for grabs if you ask me.
If the devs wont consider the Jester class at all, please at least make a bard class and the Jester hats which can only be worn by bards and give them at least 1 extra spell or attribute. I think that mmorpgs are missing this character type. It would really change the feel of the large cities to see someone standing in public and entertaining a crowd of PCs with their tricks and jokes, and maybe even playing silly songs on their lute.