Adding more summoner spells can easily impact this game majorly
Revive coming back for example, it'd bring karthus back. Zac, aatrox, zilean, sion those with revives in their kit can bring forth the whole zombie meta
Maybe add in the ones from Black market brawlers where we summoned in creatures. Instead let us summon in like portable cannon minions or something in the lane. The drawback would be it grants the enemy more gold but it'd grant you more lane pressure.
The snowball from aram could come back as a magical rock or w/e
Or even one for the supports so they aren't restricted to ignite/exhaust only. Add something that lets them pick an ally to link up to. Partner that is linked up with you gains X damage reduction based on certain stats.
Adc's get tankier and don't die in 1 second. Supports lose out on exhaust/ignite making it a risk/reward summoner. You're adding variety and lowering the damage in the game 1 step at a time.
seriously someone at Riot has to be brave enough to speak up on how stale this game is/has been
And you thing people will spare slots for something new?
but for some reason no one builds it :/ Even though they keep bitching about CC...
using his combo, W removing the spellshield and Q knocking you up, then 
or 
puts her root right beneath you, and you get blown up in a matter of second. This is the reason no one buys this item, it's just a bad version of 
(and should never have existed, since AP champions don't have an AP alternative for 
)
and 
spellshields are also better, you can choose when to use them and bait enemies with it
