Try out a bunch of items in a featured game mode again

• Make a bunch of items.
• Put them onto summoner's rift.
• See how well they work.
• Implement the successful ones.

It allows the community to be involved with the game's development at some level, as well as taking some of the burden of testing away from Rito. Whilst I'm sure there are players who will be like "Nooo I want URF not the ability to meaningfully impact the future of the game!", I'm sure that there are plenty of players who would be excited to try out some new items.

These could be very "beta" items, too. Testing a new AD Marksman item? It's a purple infinity edge!