Love the mod so far - been playing with it exclusively since it came out. This and the Game of Thrones mod have my votes for first CK2 mod subforums. A few small balance issues and new mechanics I'd like to see fixed and added:
1) Tweak the pretender penalties a bit depending on where someone is in the line of succession, as well as depending on the type of succession law in place. and the age of the pretender. For primogeniture, say -50 for 1st in line of succession if its an adult, -35 for second, -20 if third. Maybe reduce each of these by half for when the pretender is between age 12-16, and get rid of it entirely for under age 12. Maybe also a slight reduction (say -5) for succeeding a parent, since those set to succeed a parent are typically more secure in their spot.
2) This is something paradox needs to fix as well, but a way to get rid of anti-popes in my own kingdom if I return to the pope? Only way I know to get rid of them at the moment is to upgrade them with the next title (bishop-count level), (count level -> duke level).
3) Probably quite a bit more difficult to do and something Paradox could add a little more elegantly, but perhaps using an event that fires every once in a while using as the "console" cheat that lets you marry someone off, a mechanic to have a hand in the selection of the spouse of minor children who you've already titled and who have left your court? It sucks having to choose between titling a minor child and losing the chance to marry him off later. You could always betroth him before he leaves your court, but that brings you much less flexibility should political situations change.