Ekko's Ult should
be like in the trailer.
He should be able to rewind time and reuse his abilities. He needs to be able to do it continuously. He never healed himself during the trailer, so why now?
His ultimate should keep the same travel back in time mechanic. It should have 2 charges useable within 3-5 seconds (3, 4, 5 respectively). It should reduce his abilities' cooldowns by 10 seconds each. I think this would suit his kit, and his lore much better.
Just my 2 cents. :)