The whole "we're gonna make botlane more than adc + supp" is gonna fail miserably
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.

. These champions can all qualify as ATTACK DAMAGE CARRIES. This isn't to be confused with Markmen, who predominately take the slot in bot lane. I've seen games actually work where people have taken Riven with a support like Braum or Nami who can provide adequare cover and CC to allow Riven to get up in people's faces and do her thing. It's not hard at all to push some melees into the role if they have a proper support to keep them alive long enough to get into the fight. We saw early last year that APCs can work in the role as well, when Ziggs was a briefly popular pick instead of a marksman. So don't knock it just because it goes against the status quo. The only reason people aren't trying it is because they're afraid to experiment and other people can be downright hostile if you break the meta.
and potentially
though they usually build quite tanky and not really have a carry itemization, so it's a debate there.
In any case, whether we call the ranged autoattack botlane carries ADC's or marksmen doesn't really matter, as long as we know who we're talking about.
I think they need a large scale of rework and consideration on ADC's items build in order to change/make healthier meta. Otherwise it's better to keep how it has been.