A crazy idea for Mark

This is a bit of a text wall, so there's a TL;DR at the bottom.

So, I recently read a thread about how Mark is a mediocre summoner spell, which was intended to serve a particular purpose (making melee champs more viable in the siege-heavy environment of ARAM), and I found something rather interesting. Here were several arguments against Mark that were brought up in the thread:

-It simply allows you to feel like you can engage from further away, while ordinarily you are merely jumping to your death -It allows immobile champs (Annie, Galio, etc.) to engage from much further than they should be able to -You can't properly follow up on a Mark unless you're a particular type of champion (such as one who has strong cc) -Basically, it mostly helps champions who didn't initially need it

But let's widen the scope from just ARAM for a moment. If we consider a map like Summoner's Rift, then I feel that some of those arguments are no longer relevant. In particular, the issues people had with champions Mark/Dashing in and dying, or Dashing in and not being able to follow up, are less relevant in a 5v5 in which team comps are often more balanced and less one-sided. The only argument, I feel, which still really holds water in Summoner's Rift is the second one - that many immobile champs can use it to set up combos that shouldn't be that easy to set up.

My question is - how is that any different than Flash?

Sure, Flash has a shorter range and a longer cooldown, but other than that, they serve a similar purpose. In fact, I find that Mark has more interesting gameplay - there's a skillshot to dodge, it's not instantaneous, and you can't just use it as a get-out-of-jail-free card.

Here's the crazy proposal - let's replace Flash with Mark in Summoner's Rift. Even if only for a featured game mode! I think it could be a really interesting change to the gameplay of the map, and it would serve (I think) a similar purpose as removing Fortify did several years ago. What do you guys think?

TL;DR: replace Flash with Mark, see what happens, even if only in a featured game mode. Maybe it could improve the game.