Throwback/Time capsule (game mode or feature in existing, non-Summoner Rift game modes) Idea

Hi. Since there have been so many reworks in the past years, i've been thinking of an idea that might have some implementation opportunities, one of such being a new game mode (or integrated into one of the existing game modes, take URF or other rotating game modes, for example, to spice things up):

The ability to play the old, pre-rework versions of champions (granted, some balance changes would have to occur, but this isn't new, as in the recent season, URF had a wide champion-balance changes specifically meant to address the game mode).

I'm visualizing, something in the lines of 'fighting arcade games' where you unlock different characters as you progress, in this case, older-version champions, first by playing the current version of each champion, then continuing to unlock the reworked versions. Ryze would have to be a boss, having 3 reworks (is it 3?) by now, having to unlock each of them, stage by stage. Perhaps this could fit into some 1v1 game mode? I'm not sure, the idea is stil lvery abstract. The script of a new game mode does not really limit the idea, as it could be implemented in many different ways game-wise, both in a new mode or ARAM, ARURF, URF, etc.

The core stays simple: the ability to play older, pre-rework versions of existing champions.

I think this would prove interesting both to new players who have not played the reworked versions beforehand, and of course, to veteran, multi-season players, giving a feeling of nostalgia which we all crave from time to time.

This would require other tasks to be performed, of course, such as some sort of a "power balance overview" in regards to older versions with new ones, but as long as Summoner's Rift isn't involved, I guess not much meta-balancing would be necessary with these old versions.

Thank you, Eeetch