Rune system could probably stand to evolve somehow...

though I'm content with it.

However one thing would help me field more optimal combinations than the 20 I'm capped with (I want to run more combinations!)

Split each rune page into two parts. A left part of the page with the marks and quints (these are usually your offensive stats), and a right part of the page with the seals and glyphs (usually determined by your enemy lane matchup and team composition). Then in champion select you can use any combination of the left and right group you setup.

It's a non complicated QOL change for me. The "downside" is Riot might not need to sell 20 rune pages. And it doesn't bring anything new and exciting.

It's just so annoying having to make duplicate pages for a select group of champions based on the enemy team composition. My first thought was to eliminate resistance runes, but uprooting those could cause balance issues. Having tanky rune options is great, but not if generalist hp or damage reduction runes are overpowered or underpowered. Resistance runes at least get penetrated later in the game.

Maybe in some distant future when rune system does get an overhaul something like this will be considered when setting up offensive and defensive options.