Improvement to Quick Silver Sash's active(Or possibly Mercurial Scimitar)

Hello board browsers, league enthusiasts, and hopefully a Riot employee or two.

I would like to propose that the item, Quicksilver Sash, is changed so that, while it still works exactly like it does now, there's also a small window(small as in about .25 seconds or less) where champions are completely immune to crowd control after using the active portion of Quicksilver sash. Note, I am suggesting the champion would only be immune to crowd control, and not immune to all debuffs.

Context behind this change is that I feel League of legends is currently slightly lacking in counterplay to the crowd control variant of knockups and displacements. Quicksilver Sash could potentially become a much more enticing buy if it gave a counter to a Vi or Nautilus ultimate, or became a clutch way to save yourself from a Blitzcrank grab. It would still lack the ability to save you once knocked up and or hit by a displacement like it currently does, while rewarding fast reactions, and possibly forcing meaningful choices to occur in the event that the enemy team has a mixture of debuffs and knockups. For example, if the enemy team has a Zed and Vi , the player would be forced to choose between either removing zed's ultimate, or stopping Vi's ultimate from applying crowd control.

The only real problem I can think of with this change is making a CC focused champion like Nautilus lose his usefulness too early, although I can't say for sure if that would happen unless the idea was tested a bit. However, if that was a problem, this change could apply instead to Mercurial Scimitar , an item that is almost never built unless you find yourself needing the Quicksilver Sash active and having five items already built. This change could potentially make the item a good strategic choice earlier in the game, increasing item diversity without dramatically shifting the meta.

Anyway, that's my thoughts. I'm entirely open to any opinions, and would love to hear some thoughts on the suggested changes possible effects on the game, and whether it would be a positive or negative addition to League of Legends.

TL;DR Make Quicksilver Sash, or it's upgrade, Merucrial Scimitar, cause immunity to crowd control for a very brief amount of time after use of the item's active effect. About .25 seconds or so, to give an amount of time.

note; sorry for the abbreviation used in the poll, just in case of confusion, the third option is if you feel the change would only be positive for the game if it applied to Mercurial Scimitar, and not Quicksilver Sash.