My guess, is its not done quite yet but they hope the final round of beta testing might have it ready with gawd knows what final powers?
Since its a hero academy, my guess is its to retrain or reroll existing heroes in some form. When the Telluria OP problem 1st became ridiculous the thought was they may allow you to random reroll a skill on a hero in exchange for crazy gem count and possibly hero feeding. That would allow you to empower an existing hero with 1 new random skill (likely youd have to subtract a skill to equalize it). So if you got lucky you could add say Hel’s mana blocking to a different hero and that would have allowed people to defeat the Telluria OP issue finally.
BUT, thats been tentatively solved since they are preparing to nerf a pile of heroes including Telluria, and also buff up a big pile that had issues and nobody would use them (Margaret made the list! I fed at least 3 or 4 of Margaret already, though I did keep one I levelled and have NEVER used her even once!).
Strange that Heimdall didnt make the nerf list, though he is sorta a 5050 split. His slowness coupled with his limited spectrum does allow him to be beatable if you are a little careful, you just have to watch your tiles and not let him fire twice (Which isnt that hard with a slow hero) and he can usually be managed. Especially since hes often not a tank so he can be worked around. But Ive faced a few Heimdall tanks and seen the wing heroes reach 2000 health! THAT is a PITA! But its not common so it is what it is.
There was a blog post from SG that said (and it was a blog from months ago so cant be depended on to still be accurate) that trading heroes was NOT going to be the function, implying that the hoarding of 4 and 5 stars in hope of TRADE 2 FOR 1 HEROES would allow us to all upgrade our dupes to useful new names. It was said that absolutely wasnt gonna be the case. But till we see it, who really knows?