Summoner Spell Exchange

Just a thought. Do you ever think that there will be a time that in certain late game scenarios that once you hit level 18 you could change out your summoner spells? I know this might sounds like an awful idea but never the less a fun mechanic. Say you hit level 18 and you took flash/ignite early game as a mid laner but with this nifty little option you could trade out one summoner spell per game for a cost of 8000-10000 gold. This would not only force you to wait til you are 6 items but if you did make the choice to save up for it you would be missing out on at least 2 full items (who is going to do that?). Just throwing the idea out there seeing as how league is all about change and adaptation. Btw still waiting on a skin Riot.