In Exoprimal (a PVE game by Capcom), you control exosuits, who act basically as OW heroes in the fact that they have a primary fire, some skills with cooldowns, and an ultimate ability, to kill dinosaurs in PVE missions that can have smaller PVP segments sometimes. Today, Capcom updated the game with Title Update 1, which added 10 more exosuits to the game, called alpha variants, unlocked when you reach exosuit level 20 with the corresponding one (i.e Skywave unlocks Skywave alpha). I think this could be an interesting point that Overwatch can easily incorporate into the game.
For instance, in Exoprimal, Skywave is a flying exosuit who can fire small spheres to the ground that do damage+healing on area (think Baptiste healing + Echo sticking bombs combined), plus a soundwave that is thrown in a straight line, a skill to impulse and fly (similarly to Pharah) and a vortex that attracts (similar to Zarya ult but toned down), and an ultimate that stops time for a brief period. Skywave alpha variant changes the primary fire to summoning thunders in two ways: big area for less damage, or charge to do big damage in a smaller area. It can also fly in a different pattern, but the rest of the skillset is the same, including the ult. Supposedly beta variants are also planned for Season 3 of that game, this is, 3 possible alternative skillsets for every exosuit.
My point is, maybe this could be implemented easily into Overwatch, like, for instance, allowing certain heroes to have different variants of skillsets to choose from. For example, you could have a Moira with the original skillset, and a variant Moira with the discarded rework to the orb which weakened enemies when impacted. Or the current Bastion + the original stationary Bastion with a different ult. Or Young Hanzo using a blade as a weapon instead of a bow as “primary fire”. Difference with a rework is that you would still have the other option still available to choose.
As the dev team already implemented the hero progression and will include hero mastery missions, you could ask for a reasonable hero level to unlock this variant, and thus, give a meaningful reward to skilled people with that hero. They were exploring something like this with the discarded talent tree to further customize the hero for PVE, but it would have a smaller scope and be useable on PVP.
The most obvious issue to this system is a possible competitive imballance, as people would not have access or knowledge to all those variants, but they could get implemented slowly (not all at once like Exoprimal) to ensure little distruption to the meta, and could fill seasons without new heroes adding these (with a possibility to unlock them in the battlepass too i guess). It would be like adding a new hero like Illari, but with less devtime, as it already uses a currently developed hero to simply modify some of the skillset.
I think it could be interesting, but i don´t know what other people might think of this idea.