So what you are saying is that in order to be satisfactory in this case there would be a need for a mechanic to address the inordinate length of turn the character would have, so that the other players don't feel like observers?
Among other things. I think a class like the Swiftblade is nice for demonstrating another problem here - most games are balanced according to an action economy and for most games that economy is very brittle. None of the Swiftblades abilities actually give them true quickness until 9th level. This is because someone noted that the 3.0 Haste, by breaking the action economy was roughly as powerful and desirable as most 9th level spells. 3.5 haste considerably tones it down, and the Swiftblade simply is a class that provides alot of hoops before you give it back. And even then, it's not 'super quickness', it's just one extra action a turn. It's not even twice as quick, much less orders of magnitudes quicker like common superheroes or even for that matter a sci-fi character like the android Data.
To step out of D&D for example, let's look at a system like Mutants and Masterminds that has to take on this problem head on. An 'average' PL 10 superhero with level 10 Quickness, can do something like 1000 actions per turn. Now to think about the scale of this problem, consider that in an average adventure, your character probably doesn't do more than 1000 specified actions over the course of the whole adventure. Playing this trope straight, the level 10 Quickness character can solve the whole mystery and report back to the party while everyone else is still opening the door to the superhero headquarters. Sadly, said actions don't resolve nearly as fast in real life as they do in game terms. Played straight, they will also take just as much of the session to resolve as it takes to resolve an entire adventure.
So even a game that provides the mechanics for doing it openly advises considerable caution with superquickness, and not only that, it enforces arbitrary limits to the impact of speed on the action economy. For example, regardless of how many actions you can take, you still can take no more than a single attack. I can punch everyone with in 50' simulataneously, but for all practical purposes I'm only allowed to punch each once (though I can flavor it as something else).
So, again, what I'm saying here is that regardless of the system, this is hard. It's easy to say, "Sure, you can take multiple extra actions per turn.", but it turns out that that isn't actually a solution to the problem.
Since you did say in your next post that this is not what you meant - although it sounded like it to me as well - could you please expand on what the "perfect" mechanic in this situation would need to do to be satisfactory to you?
The perfect mechanic would make a person who isn't funny or witty, funny or witty when their actions were narrated. I suggest that such a mechanic is difficult. I also would like to note since for some reason there seems to be some confusion, that I don't think such a mechanic is necessary in order to play a funny or witty character, as all you have to do is be funny and witty in your characterization. What I'm pointing at here is a specific (and I think particularly hard) instance of the general problem, "How do you create mechanics that let the character possess mental attributes that the player doesn't have?"
And as I said, its much easier to create the reverse - mechanics that follow from a witty characterization - than it is to create a witty characterization that follows from mechanics. The best example I can provide of this is Elan's 'Charming Swordsman' prestige class in 'The Order of the Stick'. Elan as a class ability gets bonus damage whenever he makes a unique witty comment as part of his attack. This comment rewards a witty characterization, but in and of itself can't create one. And the narrative of the Order of the Stick provides a good example of why a purely mechanical resolution of a characterization issue like 'wit', 'humor', or 'creativity' would be unsatifisfying. I don't think Rich would get away with saying something like, "Belkar climbs on top the pile of dead hobgoblins and excercises his 'victory cry' ability to make a humerous and oddly stirring declaration", or write a panel in which every few cells he writes, "Elan and Belkar exchange humerous japes." He might get away once with writing, "Elan says something humerous that inflicts 3d6 ego damage, but Belkar protects himself with a cloak of indifference.", but only to mock the trope (and yes, I did steal that joke from someone else).
