So for Agent Carter I'm not aware of anything they could bring into canon that doesn't already fit. We got (human) Jarvis in Endgame, so he's already canon. But Peggy Carter's life is pretty vague, and possibly different after Cap' went back in time, so we can just call that canon now.
As for Agent's of SHIELD, the later seasons take place in a virtual world, the far future, the far past or an alternative timeline. So you either ignore or multiverse them.
For the earlier seasons, they either track with the MCU or do their own thing that doesn't conflict.
Now, if you're asking, should we bring these characters back? Sure.
Quake is the obvious one. She's an Inhuman so that's a small wrench but post-Secret Wars we can just call her a mutant and be done with it. Or if you want to do Mutants vs Inhumans you can still make that work, we even met Black Bolt in Multiverse of Madness.
There are plenty of SHIELD agents to bring back. The main timeline has sorta fucked itself with Secret Invasion and we only have Nick Fury at the moment. Have him go recruit some old agents. Hell have the Hawkeye family come out of retirement.