None of the leaders in Medieval Europe that tried to create a huge empire managed to make it last. 30 Cities is the territory of 3 large nations, it is unrealistic to have an empire this big, only the Ottomans managed that and we have not balanced them yet. Your arguments are not RFCE specific, perhaps you don't believe in stability at all. Allowing empires of the size of 30 cities is pretty much removing the stability parameter from the game. There is an RFC modmod that does that and eventually we may make one for RFCE, but we are not removing stability altogether. If you want, you can remove the block from the code, noone will stop you. Research penalty simply exists to make sure that nations like the Netherlands can keep up with France and England. It works in conjunction with the individual civ modifiers.