That you would only rely on positioning and kill rather than going all in and then casually flashing behind wall or out the turret range.... You would actually not be safe on stupid all in champs
It would be ideal, but then immobile champions would have no absolute means of getting away from mobile champions.
Not only do mobile champions have dashes, but on top of that they have a higher base movement speed advantage up their sleeve. So the only way to make this work would be to reduce their base movement speed to match the base movement speed of immobile champions and maybe it could work potentially. But I still think there would need to be further changes even then.
I feel like you just want to play DoTA.
I don't hate flash, I hate the fact that nowadays most champions have a some kind of escapes in their kit, added to 
itself, it being too forgiving.
Riot fucked up at the very start of the game, and it is now too entrenched in the kits of nearly all the champs to not be taken anymore. Especially with the continuous nerfing of other competing~~ keystones~~ edit: oops, "summs". Junglers that used to run Exh/Smite or laners that used to do Exh/Ignite now are forced to take Flash or not be able to function lategame.
TLDR: Flash should NEVER have existed at all, in DotA, it's actually balanced by the fact you have to spend a full item's worth of gold to get it, and even then it has limits.
