You can easily peel off the assassins with multiple point and click abilities whether it is cc or shielding
yes and this pushes both ADC and support players into a play style that is less fun for both of them. I would rather play a support that is part of the aggressive section of the team than a point-defense specialist. The fact that I can play a point defense specialist as a support doesn't mean I prefer this style of play.
"assassins are fine because you can play a less fun style and counter them", is what you are saying.
This is not the reason why bot lane is ganked the most
There is no single reason why bot lane is ganked the most. There is a multitude of reasons each contributing some portion. The argument that mid lane pick has no influence on how much each lane gets ganked is equally erroneous.
Whether you have mage mid, an adc mid or an assassin mid the junger has little reason to go top in most games. The mid lane pick doesnt influence that at all.
Gankable mid lane picks results in roaming from top to mid and roaming from bot to mid, in order to gank. High escapes on mid pick results in a much more limited roaming situation. Roamind top->mid and bot->mid is very desirable especially the top->mid roam possibility, because these add a lot to the enjoyment of the game from bot and top players...
bot lane benefits because being able to gank mid serves as a respite from the "gangbanged at bot" pattern of play. It allows bot to be agressive and proactive, which is fun, rather than playing a wait for jungler wait for the big 4-man gank style.
top lane benefits more heavily because roaming mid is a big way into the game as a whole. If top lane receives no ganks and has no objectives and donates no ganks than top lane is an island and only has limited play style. Being able to gank the mid lane opens up the gamaplay options for top lane in a big way.
If we have tanks and front line champions mid
I think you've already seen the connecting thread in my post: each and every one of my suggestions harms mid lane in some way.
The reality is most people do not want to play tanks. So this burden should be shared. Right now top is tank is an obvious solution and so is sup is tank. jgl is tank is somewhat of a problem due to clear speed. Having viable tanks mid alleviates some pressure off the other lanes.