This could work but not exactly the way you're suggesting. Some points:
1) Players can capture all the monsters no problem.
2) When you use the skill to capture the monster, the monster is killed/disappears and you get 1 point for that monster. Let's say there's 1000 monsters (because I sorta forget exactly how many there are), you can get 1000 points.
3) To have a physical item would explode your kafra storage, would need a unique item and item ID for every possible 'catchable' monster, and would bring up other problems addressed and not addressed yet here.
4) The system could work along the lines of the TKM monster killing script but to a more complicated degree I think. I'm not sure how complicated exactly, but it would take time.
5) It would probably rely on the developers overseas and thus what you're asking for has to A) pass 'inspection'
be doable by the developers and C) be developed and translated and brought back and implemented...and bug tested.
Which is all to say I would love to see this in game! Great idea!
How about when you finish capturing every single monster you can change your sprite to that OF A MONSTER!
Edited by Ultimate, 11 April 2011 - 04:41 PM.