I like the huge variety of different types of heroes. Two aspects I like less:
1. The number of heroes received is limited to one per turn.
2. Most of the heroes I assign to my panzers due to the specific advantages they bring. I hardly assign heroes to planes or bombers for example.

Idea related to bullet 1: Depending on difficulty level to increase the number of heroes to be received?
Idea related to bullet 2: Although I like the randomness, to have more choice on selecting heroes. For chose a unit category and then have the game decide on a random leader within that category