On Desktop it could work. On Mobile, It all depends on how much battery it consumes. Games (which usually do immediate modes) tend to reduce a 4-6 hr workload to just a couple of hours. Most of that is due to the aggressive rendering stack. Especially now with local adaptive refresh rate of the new displays...
Could immediate mode be the future of GUIs?
https://games.greggman.com/game/imgui-future/
I think so...
#notedeck
Discussion
egui doesn't render continuously so there's that
from my testing notedeck uses wayyy less cpu than the retained swiftui stack. swiftui spends so much time managing the scene graph and deltas. its one of the biggest performance issues on iOS. with a frame rendering in less than a millisecond, and it rendering non-continuously, I'm pretty optimistic about battery.