Should we be able to buy "perma-elixirs" very late into the game?

Currently, once you finish 6 items, you sort of hit a dead-end. Gold somewhat stops mattering to you, as now all you will ever really need is just 500 gold every time you back, which for someone who already has 6 items is usually just too trivial an amount of gold to spend. You end up with massive amounts of excess gold, with absolutely nothing to spend it on. Sure some champs can sell boots for a 6th item, but this already is quite rare and will be even rarer with zephyr removed, as really only adcs had reason to sell boots for a zephyr since their team peels for them naturally, with very very few mages on rare occasion selling boots for something like luden's or deathcap, usually on already mobile mages like ahri.

So what do I propose? Similar to how you have to hit level 9 to buy elixirs, you have to first hit a certain goal before being allowed to buy this "perma-elixir". Currently my 2 thoughts are either making them available at level 18, or making it so that you must own 6 un-upgradeable items in order to be able to buy them. Their only function is to give you the same stats as the current elixirs, but permanently. Their cost should also be fairly expensive, I'm thinking around 2000 gold or so, so that way you still need to continue generating gold to be able to buy them. They should also make it so that you can own other perma-elixirs with each other, making it around 6k more gold that people have to get. This would give people who already hit a full 6 item build still something to do, and would prevent having people stuck with 6k gold and nothing to spend it on. It would also be very crucial to late game, as you won't have to worry about your pot running out ever.

Thoughts on this? I think this would be a great idea and would give people incentive to continue playing the game as it should be played instead of engaging in a 20 minute long dance between teams at someone's base because everyone has hit full build and have nothing to do anymore outside of killing the enemy team and ending the game, which is why these 20 minute dances of doing nothing but pushing the waves back and forth occur.