Why this isnt a thing yet

so iv been toying with a champion idea for a few months and have partially fleshed it out, a genderless champion who much like shaco is from an unknown area, however this champion would have three normal abilities and it's ultimate would allow it to become another champion currently active on the map, from either team. more or less this champion would be a mimic of some form and its first three abilities would be nothing special just some utility and single target damage things. however once it ults it would get for lets be generous and say 60seconds, all the abilities of the champion it turns into, but not their ult (more in a sec) it would use its own ranks in the corresponding keybinding for each ability, not the champions from whom they were taken. lastly if it was able to take their ult then upon casting said ult it would return to its normal genderless form as soon as the ult finished, and its passive would be much like most rage generating champions where it outlines how it can do what it does, in this case shapeshifting into another champion. one exception to this would be that champions with other forms like shyvana or elise when ulted by this mimic would only be copied in their current form, as their ult is how they change between the forms, also the enemy passive wouldn't be copied like their abilities and would most likely result in slightly weaker versions of certain champs as a result, but that is a good thing considering if you had say two viegars on the same team. and lastly this champion would be a hybrid champ most like akali in terms of build you just have to choose who you ult carefully or youll be a puddle on the rift before you know it

personality disorder aint got nothing on this concept