I strongly feel like the right way to get mages in bot was to design new mages for bot.
The fundamental principle of the 2v2 lane was that you should take a champ that scaled better with gold than levels. (Obviously going to be talking about the farming bot role, not the support.)
Why not just make mages that scaled that way, if you wanted mages in bot lane...? There are already models of what that kind of mage could look like, with minor kit tweaks (Cassio if her E scaled differently, for example). I feel like opening bot to level-scaling mages makes it fundamentally too difficult to balance those mages, because being at balance for a 1v1 lane would make them overbearing in 2v2, and being at balance for a 2v2 lane would probably sink their 1v1 laning. (This is especially true of champions like Swain that were designed for a solo lane but have parts of their kit that are very exploitable in 2v2 laning -- balancing swain for the easyproc passive he gets in bot should leave him unplayable elsewhere.) Champions that do well in both 1v1 and 2v2 lanes simply choke out the existence of champions that only do well in 2v2, both through their laning and their flexibility in pick and ban.
In general, marksmen were dominant bot by game design. There are few other champions that scale into hard dps carries other than marksmen, and those few exceptions that existed (Azir, Ryze, Cassio) were given kits that shoehorned them into solo laning. Opening bot to mages is literally violating swaths of design choices across item designs and kit designs. It looks like a decision done without understanding the basic logic behind why mages don't go bot to begin with. The result we're getting -- marksmen largely being choked out bot -- is only what you'd expect when their base stats are gutted so that they don't lane well against champions that scale with levels (or lane well at all, to be frank -- why do they need lower hp5 than anyone else in the game?). They'll just lose in the 2v2 and become useless. Without the option to laneswap and safely farm a hard carry in a meta like this (an option Riot removed years ago), marksmen are just bad. You sack too much tempo. You're playing a control deck without any real means of stabilizing into an aggro deck and hoping to win. There's no reason to play a marksman unless you think the other team just can't take advantage (and is thus worse than you, period). The point of running a marksman was basically just removed because if you can't scale at least somewhat reliably to stabilize the game (and you can't against mages designed to solo lane right now, since you can't laneswap), there's no reason to attempt to scale.
If Riot wanted mages bot, they needed to make mages that played by the same rules as ADCs. But they didn't take that approach. And now we're seeing the fallout.
