I think this topic should be revisited -- I do think a level cap in general is a bad idea because it completely stops the idea of character development, but so is unrestricted character power.
I think a diminishing returns system would be ideal for this. As an example:
After level 20, you should stop gaining hit points and psi points per level, making it so that only getting your +1 stat point every 4 levels can increase your health and psi pools. Or, it could be reduced to a flat 2 hp/1 psi boost per level after 20.
After level 24, you should only gain stat points every 8 levels and new feats every 4.
After level 30, your skill point gain should be reduced to 10 each level.
This would prevent characters from being too powerful too soon, but at the same time, if one were so inclined, one could eventually build a character that is a master of everything after multiple playthroughs. If you play the same character for 700 hours, that character kind of deserves to be an OP superman of some sort, and by then you probably have already beaten the game, so why not?
The "import/export character" function also serves as a way to prevent players from being stuck at the game due to "improper" builds, and those characters will reach a hard cap sooner into the game, which would only compound the problems they have near the end of the game. Uncapped but diminished level improvements would still make these characters viable to play the game through, if unoptimal.