I think it would be more realistic to expect or ask for them to make mystery champions a permanent option rather then rerolls.
With the BE system, shards are everywhere so the value is high to reroll in the same iteration we had previously. Reroll works better the less low cost champions you own, so its not that much of a benefit to newer accounts trying to fill their pool.
BE changes have a lot of aspects that favor newer players, I'm ok with this as its a hassle to grind champions. Reroll was great, I used it to unlock pretty much every single 7800 champion riot released after they added in champion mystery shards to the store, but that discount for me was not available to a lot of players and every season of IP previous to hextech crafting was a long IP grind where it would take days to weeks to unlock a new champion. Plus if you wanted to be remotely viable you needed runes. Then when pick order was how roles got assigned you needed to have multiple pages of runes to function for various classes and roles, so that was a grind as well, I think it took me something like 8-10 months to grind rune pages from IP to not play ranked with a disadvantage.
Bringing back reroll will mostly help mid content accounts as they have the option to get 6300 cost champions at 270, lets be clear that's a freaking huge discount around 95.5% off (ish) . I think you need to take a moment and ask yourself if what you personally want to see is reroll brought back or for riot to just make every champion unlocked for all players. Its ok to want free content and to have a better pool, its silly to ignore the years of grinding that have existed.
Tldr, a majority of league existence the free to play users have had to grind hella for a vast majority of the games existence. Riots added some features that made this better, the current system is better for new players.