Hero rosters
Everyone’s needs are different.
Some players are happy receiving any 5*, even if it’s Atomos or Khagan. Possibly because their roster is small. Possibly they just don’t care about viability and are happy to have another 5* hero.
Other players just want chances to get something they don’t have.
I am F2P. But I have almost all of the classic 5*s already. The only relevant ones I’m missing are Vivica and Sartana. I don’t have Richard, Elkanen, Elena, and Azlar either, but I’m not really desiring them much either.
I’ve read posts in the Beta Lounge from players who already have all classic 5*s too. So if the Hero Academy just gives classic 5* heroes, that makes the Hero Academy of very limited use – P2P wouldn’t bother, and eventually will also become useless for C2P 1st and then F2P.
Including non-trainable heroes
I really think that for HA to not be a flop, it really needs to include heroes that are desirable, even if the chance of swapping cards for them is low.
Including old HOTM like Alberich or Perseus wouldn’t break the game, if the odds of getting them are low and if the time it takes to train them is too long to do it repeatedly.
This way the building has a use. Make it such that only a 5* hero can be traded for the possibility of a previous HOTM.
As @FraVit93 suggested, this model also has possibility to include more heroes, once they become old themselves.
P2P stay ahead anyways – they can use their duplicates to get heroes they missed, or save their duplicates for when HA features a hero they want. And keep spending gems to chase the newer heroes.
Gem fee
I would not like a gem fee on HA, but I’d be more okay with it than with AL… After all, I already spend my gems doing summons.
But I don’t really believe it is required either.
If it takes 7 days to possibly exchange a dupe 5* for another 5*, players are still going to spend their gems in the in-between periods. Even if it includes old HOTM.
Gem fees can be completely avoided too by limiting the amount of special heroes in the HA. It would be okay if just old HOTM were included – keep the newer shinier heroes in summons, until they become old.
In other words: