I'm amazed at how selfish people are and how they only think for themselves...
comp people:
REMOVE EXP, you have one south of cerulean! my level 50 leveled to 135609 by mistake! :(
non-comp people:
I got 10 pokemen leveling at the same time with all my exp shares and daycares, it's your fault if your level 50 leveled up.
First of all: i don't do comp. I love the daycare exp systems, i can train 4 pokemon to level 100 at the same time a lot more efficiently than in the games.
It would be selfish of me to say screw that, either they're careful or they shouldn't breed.
If i did comp. and i had a good IV'd and natured level 50 i wouldn't want to use another pokemon, and i'd still want to keep the level 50 without worrying too much.
Anyway, as it was suggested before: instead of disabling the daycare exp i'd suggest adding an option to whether you want your pokemon to be leveled or not. Everyone is happy that way and it's not hard to implement.