If instead of {mapIm maH chaH je} for "we are different we and them", I wrote {pIm chaH maH je} for "they are different they and we", would you accept this too as being correct ?

No. I think maH chaH je is a kind of maH, not a kind of chaH.

It occurs to me that this is exactly the sort of problem that Klingon lets us avoid: mapIm maH; pIm je chaH. This is probably the "most correct" way to say this.

-- 
SuStel
http://trimboli.name