Swapping ISO for Hero Points

Let me tell you about the time there almost was.

(story time with an old-timer).

Back before there were shards or champions... we had: the 1* Token Store.  This was a store that you could pay 500 ISO and get a 1* token, just like the ones you can win by clearing certain nodes in PvE or by clearing certain progression levels in PvP.  The tokens that give you a 1* most of the time, a 2* occasionally and RARELY a 3*.  The ones you can no longer buy at all.  Yup... those tokens

"Where did they go?" you ask... "When did they remove the ability to spend ISO to buy them?"

Well... it got removed when the "Champion" system was implemented.  It was removed then, specifically, because for anyone with a sufficiently developed roster, doing massive amounts of pulls from the 1* store was the fastest way to get 3* characters.  The 1* store gave you a bonus cover whenever you hit the RNG jackpot and drew a 3* cover (giving you 2 of the same cover).

So... how does this tie back into the OP's question?  Well... there was also an issue with dilution and "vaulting" at the time.  It was hard to get specific characters, especially older characters.  This was designed scarcity.  This was supposed to keep the whales playing the gacha game and purchasing HP (I don't think 5* and CP was a thing yet, but my memory is a bit hazy on that and the timeline might be a bit off).  The new champion system allowed us, the players, to effectively sacrifice ISO (by leveling a second character instead of selling the covers for next to nothing) to champion 2 and 3* characters for the rewards (ISO, HP, and more tokens) and to eventually sell them off for ISO and HP and start the cycle over. 

The management of the game immediately saw that if they left the 1* store in, the system could become a near perfect cycle of spending ISO to get HP and max characters that could be sold off and the cycle started anew that they had to remove it or it would collapse the entire game economy.

The cycle is still there, but it is self-limiting in that the rewards we get for the champion farm do not fully pay for themselves and need us to actually play the events in order to get enough resources to keep it going... that or pay for HP to buy tokens directly.  If they hadn't removed the store and left it as is, farming the champion system would be a LOT faster.  It'd take days to fully champ 2*s and a month for 3*s without spending anything to support the game and it's staff.