With the focus on new demigods and maps (as it should be) I feel minions and creeps have been left out in the cold.

Demigod has a great system in where you can buy idols from the shop. There you can determine what type and the power of your minions. Such a flexible system is just asking for an upgrade.

More idols for more minion types - things like

Ghost - minions who stun creeps

Goblin Jesters - warp from one space to the next

Hags - suck the life out of others and gives it to the Demigod.

Will - O - Wisp - sucks the mana out of Demigods.

Baby Unclean Beast - spit everywhere, slow long term damage

etc ....  This could also apply this to the tower for more creep types.

How about going to the tower and getting upgrades to change the way creeps react

Priest -  To retreat back to the next wave when they find themselves alone. Longer shot power. Shields

Angels - Resurrection ability (Munashiimaru idea), Kamikaze - fly into light towers when dying. Defend light towers from attack.

etc ...

If you have more options for minions and creeps in the game it might gain a whole new dimension.