I'm sorry for being négative, but Honestly...
We're gonna build a new botlane and make the adc mains pay for it, it's gonna be great !
No. No, it's not. It's never gonna happen.
Do you really think you're gonna be able to change botlane to include anything else than adc's?
I guess you at least know why the repartition of roles is as it is right now: adc's and support not only complement themselves extremely well, they also beat pretty much every other combination in lane, while having great synergy with this lane setup: adc's scale extremely well with gold and less with levels, supps have great kits that dont need a lot of resources (gold or exp) to work well.
How are you gonna make that Work? Do you plan on changing every other champion's scaling and completely fuck their balance state in other lanes to have them somewhat work botlane ?
How are you gonna do for nonsupport melees? Make targon melee-only and broken overpowered, something along the lines of mordekaiser passive, aka higher exp revenues ? You know that's gonna either make melees dominate botlane, and/or make tank melee supps just way better than everyone else at the expense of enchanters or mage-like supps (brand/zyra)?
I don't see it ever working especially since adc's and supps have been ridiculously powercreeped through reworks,buffs to kits and itemization.
It's like an impossible nasty optimization problem. There are too many constraints, you can't solve what you wanna do without breaking everything else.
I mean, consider that as a challenge if you wish, it would be literally insane, incredible if you manage to make a lot of other champions work bot. But Honestly, in the current state of things the only thing I can see work bot would be a dps mage with high item scaling and similar characteristics as adc's.. Maybe azir? But that's it. I would be really glad if you proved me wrong. Really. But I don't see any way you could ever do it without breaking the fuck out the game.
And when I see the balance is determined by people like ricklessabandon for instance, the silver guy that without ever consulting Yi mains proceeds to do a random meditate change that solves absolutely nothing, realizes his change is garbage, reverts and does a pretty much straight damage buff while royally ignoring the community suggesting highlander reverts and changes like removing alpha Cast time to solve buggy interactions, basically like the champion is not worth his time.. And after those kind of pathetic balances, Riot talks about being able to do an insanely huge project to make botlane more diverse, which is infinitely more complicated... I'm sorry but I can't trust you.
I might be biased, and wrong, sure.
Please prove me wrong.
Sincerely, a cynic player.