Ignite is easily my most hated Summoner Spell in the game mainly because of one reason: It's an instant targettable skill that to use it requires you only to be in most ranged champions' aa range from your target to mark them for "certain" death.
I've been pulling my hair out countless times over the endless situations where I died while trying to make a cool outplay (ex. dodging all of the opponent's abilities and shit when being really low on hp, thus somewhat baiting him), simply because I could not in any way stop him from Igniting me. Nothing is more infuriating to me than looking after such moments at Death Recap and seeing that the only thing that dealt damage to me was Ignite - something I couldn't play around EVER.
So my idea for giving Ignite at least SOME chance for an actual counterplay is simply making it into something (that could potentially also make it a buff in certain situations and make it more viable for some other champions too) like THIS:
"Your next damaging ability that hits an enemy champion (Paste Ignite's current effect here)"
This is it. All it needs. It makes it so you can actually play around it at least a bit. It could make some weird conflicts with AoE abilities when they hit multiple enemy champions at the same time, but Riot would sooner or later fix that interaction somehow (I'd hope, at least).
It could easily be a buff to many long-range champions (Xerath igniting you with Q or R, Karthus' R making some weird applications of the possible AoE-Ignite issue), but, in my opinion, it would still be a lot more healthy of a Summoner Spell.
The auto-attacking champions could get fucked by that change, but I honestly believe that most ADCs shouldn't use Ignite anyway.
Changing Exhaust, in a similar same way, could also be a good idea, now that I think of it.