Is there a story post somewhere? Or do you mean the general idea?
I think it's completely within RP to play a madman. Why not?
Just be careful not to let him turn into a PvP-only char and think of a good reason for his behavior. If he's "simply mad", maybe you can think of some traumatic experience that drove him crazy.
And I'd recommend playing him very different all the time - unstable! Sometimes just aggressive and blind with rage, other times maybe afraid of things that aren't there or even like a completely different person (nice, for example:D). There certainly are a lot of possibilities.:)
as he stands now i've still got the neutral ID until i finish mapping...then i think i'll have to get the pirate id since the terrorist id is out of reach. I'm just not going to play him as a pirate...cause he's not. i'll prob not bother with PC traders because asking for payment is out of RP for Mon'Star. which stinks cause homicidal maniacs shouldn't have to avoid killing anyone but i have to work with what i got right?
it'll still take me a few more times of playing to finish mapping, i only get to play 1-3 hours a week maybe more on the weekend so it's taking a while to get him ready.
so when if you see me laughing maniacally in system chat you'll know i'm doing my best to wreck havoc. i've not PVP'd yet so i'm sure i'm horrible so you'll prob not have much to fear from Mon'Star till i atleast get some decent experience.