random thought. what if we have (ranged only) boots that increase the AA range as long as you have them? in case thats too op, make it a summoner spell that increases it for xx seconds.
i really like 
you get that pretty hard to predict bonus range aa in. but its only 1 aa. and then you have to let it charge again. i hate that you have to charge it so long its so annoying.
Solicitude3 votesThat would be broken, either as a summoner or boots. The only reason is not broken its because its just 1 aa and then it needs to be recharged, which takes, as you said, some time. 
(with rockets) 
(lvl18) all have very long range, 
can also increase their range quite a lot, this long range allows them to be safer in fights than other ADCs and most mages. If they had further increased range, even if that would be for 5 secs, it would really make them untouchable.
Arammus1 voteswell i have to agree with you. i wouldnt say untouchable tho. a lot of the "perma meta champs" could still reach you. zed with his flash w r. lee with a q on a teammate + w flash r. current akali with her 3 ult jumps. kha's evolved jump. rengars ult. etc. these could steal reach you. but i guess youre right. it would be too broken
Solicitude1 votesYou also have to consider that you are not 1 person just sitting alone on a lane watching the stars. Without even accounting an increase at an ADCs range, if you have at least one "punch-bag" protecting you, all of those assassins will struggle to reach you from the front (assuming you play it correctly) and you will probably have a support shielding you if any struggler manages to reach you. With an increase in ranges the threat on an ADC would be severely diminished. Just remember, quite some time ago they nerfed the bonus range was getting from her passive because her max range at lvl18 was making her virtually untouchable.