Mid is already the most snowbally lane and has the largest impact on the game. Making their tower weaker would just exacerbate that issue. A single jungle gank in the early game on mid, leading to first blood tower, opening up the map for the mid to roam with the jungler early... it's just a disaster waiting to happen. I think Riot said first tower blood already has a 70%-ish win rate? I'd imagine that'd go up by 20% if it became mid lane...
Mid lane would be relegated to champions that can safely waveclear for a long time (so that they can't die to ganks and can keep their tower alive and thus deny their opponents opening the map) and in response junglers would largely be relegated to those that excel at tower diving so they can kill the mid laner anyways.
I don't think Riot demands a tower being weaker. They only made bot tower weaker to deny the lane-swap strategy that evolved in the pro scene. I think that strategy may be over now, with all the jungle changes that happened since then (at the time jungle xp wasn't tied to items and top laners were taking TP and doing a camp at game start then TP'ing to lane at level 2 to avoid a hard level 1 matchup. Then I think that got removed with the jungle XP and they started doing lane swaps to avoid the bad top lane matchups instead. Really, everything revolved around how bad counter matchups were in top lane, and I don't feel like top lane is in as uneven a state anymore).
Basically, Riot won't stop the bot lane tower being weaker unless they're confident that the meta wouldn't return to mandatory lane swaps enabling a better scaling top laner to avoid a bad laning phase. I think the meta may sufficiently be in a place that would allow that and would like to see Riot try it, but I doubt they would anyways.
