I think Riot has an oppertunity to upgrade rentals in crafting.

With the release of level up capsules and the shards it drops, the turn shard into rental feature could be upgraded a bit to encourage folks to test out new champions. Currently rentals remove the shard from your inventory. Personally I think it might encourage players to try new champions out if they could rent them and still get some BE after the rental duration ends, and have the option to upgrade to a permanent at any time during the duration rather then the instant removal.