The current feature list I have planned is as follows:
Changeling civ with some more changelingish powers, I have the basic creature done, but they're quite plain at the moment.
"Pinkie Pie" earth pony industry, add bakery and food buffs, some slightly more advanced food options
Add some more plants, maybe look into plant balance, add some variety for diversity and spread them over the biome types.
Unicorn magic - the unicorns have a LOT of castes who's special ability is magic, might want to give them various degrees of spells, from the simple, more telekinesis, to some interaction based stuff. I know I have at least one magic healer class which definitely needs a spell.
Elements of harmony - I had an idea for some advanced interactions that would emulate the elements of harmony.
As i have 2500 castes I can pretty much seed the caste list with potential elements, then use the element of magic as the trigger, giving it the ability to activate one pony of each element. Once activated the elements would get some aura buffs that would effect everyone, but the other elements in particular, growing in strength the more elements are nearby. The only problem with this is the possibility of multiple elements of magic. I tried tying the element to a government position so that it would show up after X amount of population like a baron, but this seemed to tie into the land holder stuff, needs more research I guess...