If Flash becomes a built-in summoner spell, like Recall

What happens to the balance of the game? Since we've pretty much ruled out removing it, how about just handing it out? Since almost every champion takes it (except for maybe half a dozen, all of which can do fine with it anyway). Will another single summoner spell take over? Will it actually create diversity and choice? Would it ruin the game or improve it? Thoughts? _ (Keep in mind this can go on the PBE as an experiment to see how it actually plays out.)_
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