One thing that I have to say about the jet thing, it most likely was a mistake. Even interplay made that mistake in fallout 1, it mentions jet before it was even made. So yeah, mistake.
Bethesda has forgot about Jet not being pre-war multiple times, such as putting a shitload of Jet in a vault that'd never been opened. They sort of disregard lore wherever they feel like it and sometimes that's okay because they improve things but the whole jet thing annoys me.
I'd be completely fine with Power Armour suddenly requiring Fusion Cores if there was a lore reason for it, I'm one of those people who enjoys the lore of a universe more than the content usually, so changes like that just bug me.