I agree that putting Tank on E would be a really nice rework for him, making him more fun to play and more skill-based. I don’t quite agree with the route you’ve gone with it though…
I’ve compiled some ideas from other Bastion mains, as well as some of my own into a Tank on E thread here: In-depth "Tank on E" rework for Bastion
In this one, the tank shells do 120 damage (reduced to 75 damage past 40 meters), same as a Pharah rocket, Junkrat grenade, Helix rocket… they also have a slightly reduced splash radius, and his ammo reloads similarly to Doomfists gun. He has 3 shots, and they reload at 1 per 2 seconds.
Sentry mode is changed to have a similar spread pattern as Hammond, 200 ammo, 1.5x multiplier headshots, and a 2.5 second reload time.
His ult buffs his different modes in different ways, and lets him transform between them faster to allow more varied use of it.
Ironclad has been removed as a passive, and is now only applied when repairing. It is now able to be applied in Recon mode as well, but again, only while repairing.