TL;DR: if you DO NOT choose Flash as any of your summoner spells, the others should get buffs and additional functionalities.
We all know that Flash has been a staple summoner spell for over half a decade now with [only around 4% of people not using it at the moment](http://na.leagueoflegends.com/en/page/keybind-wars-which-key-best-flash) and we all know why. It adds play-making ability both defensively and offensively, enables champs without gap closers to get away from divers, enables the repositioning of spell hitboxes (looking at you, Alistar, Lee Sin, Riven, etc.) and many more things.
Now, let's see what Riot has done in the past to systems that are available to every summoner and champion that had a clear best choice: Masteries (Keystones). Most people still remember the League of Thunderlord's when everyone and their grandma took it just because it was superior to all others. So what did Riot do? First, they slightly nerfed TLD, then they strongly buffed the other choices - and even though most champion subclasses use one single Keystone per class now, other choices are at least compelling enough to pick up.
The first part of that has already been dealt with by Riot: Flash has had its range and cooldown nerfed multiple times, but that didn't stop anyone from pretty much always taking it anyway. So how do we make people use the other summoner spells?
I think the answer is simple: We buff the other ones IF you are not using Flash at all. Hear me out on this one.
We know the technology is already there (™) to detect if a summoner chose Smite to allow him to get the jungle items. So there is probably also a way to detect if none of your chosen summoner spells is Flash.
The buffs/additional functionalities I'd propose for the enhanced summoner spells would be the following:
- Ghost: total duration still 10 seconds, grants +75% movement speed when moving towards enemy champions for the first 3 seconds which then decays to 50% (at all levels) towards champions, otherwise identical
- Exhaust (drop the resist shred on base Exhaust): grounds the target for the entire duration
- Ignite: reduces target resistances by 30%
- Heal: increases the movement speed duration to 3 seconds
- Barrier: grants 20% damage reduction for the duration
- Cleanse: renders the target immune to all crowd control for 1.5 seconds
- Smite: recharge time reduced by 10 seconds
- Teleport: grants a two second +50% movement speed boost after usage
- Clarity: for 10 seconds, the next three spell casts will not cost any mana and will return their mana cost to your mana pool - 120 second cooldown
Tell me what you think (especially Rioters, if you guys are reading this)! ^-^