Request for a Rune Page that we can modify during Champion Select

I've always wanted a rune page that we could modify at champion select, but looking at the end game stats for the games at Worlds make me want to even more so. You look at the rune pages that they have and I can't help but think how specific to the champion the page looks, and imagining that they must have 2-5 rune pages setup for their key champion picks. As someone who likes a diverse champion pool and can't rely on a set role in any solo queue game, this is quite frustrating to not be able to do this effectively, even with 20 rune pages.

Here's an example: http://matchhistory.na.leagueoflegends.com/en/#match-details/TRLH1/1000380094?gameHash=99c3ef0043f3fb35&tab=builds&participant=2

Look at Lee sin's runes. It's specific to that champion, although it could be viable for others. If you truly want to min-max though, you wouldn't have that setup for any matchup.

Mundo's is a perfect example that he has a rune page SPECIFICALLY for champions like rumble. You couldn't run that effectively on any champion, let alone against any matchup. Even Lucian has a particular rune page specifically for that mana heavy ADC.

What is the reason that we don't have rune pages that have the option to modify during champ select like we do with masteries? Some would argue because Riot makes money off of rune pages, but the weak counter argument to that is Riot is a player first attitude. My counter argument would be an expensive rune page that players could purchase to modify at any time in champ select.

It's not feasible to modify rune and mastery pages every single champion select, but that's why having set pages are useful as well. I would personally love this feature, and I'm not sure why Riot hasn't made it a thing yet.