I don't think that the flash and molly need that kind of buff, bc they have different use options/animations (flashes' got left and right throws, molly's got long and short range), but the wall only goes foward, no other option other than curving it. The best they can do about it is reduce the equip animation for the molly. I think that they've got to remove the wall's equip time, and maybe adding a new throwing option for the flashes, like a foward long range Kayo kind of flash, no gravity so it just goes in 1 direction, and maybe bounces and stops when it collides with a wall, like his actual flash does. Also it's a good idea to give him more healing from his molly and wall, since he's got no movement ability it's a good idea to give him a way to recover from a gunfight. It's definitely a more passive approach to a duelist, but it's the only way to make him playable.
If Riot adds everything that I've said they could save Phoenix, as he doesn't need a lot of buffs to be a better agent, he needs BETTER MECHANICS.
And no. Long range flashes would not make him exactly like Kayo, there's different ways to implement new mechanics to basic agents. All of this could save Phoenix from being useless and eventually, unplayable.