Start on "Hero".

I just like the design of the Academy, and the "evilness" of the demons, but unfortunately, it's difficult to play as these two factions.

Well, I wouldn't say that playing as the Academy is difficult. There's a period when you have a lot of troops, but not enough miniatures; during this period, the mage hero is the weakest.
And the Academy would always benefit from a powerful starting spell, which is also a strength of the Orcs and the Necropolis. In the Chaos guild, it might not even appear.
As for the Inferno, it's not so much difficult to develop, but rather a very long and tedious process.