Contrary opinion:
Nah, casters don't need 'em. The feats are one of the things that equalize the linear-martial quadratic-spellcaster, their equivalent feats at each level are things like 'well I can completely change reality yet again today', so we don't need to get into the 3.5/Pathfinder arms race to 'see how many splat books we can publish to make casters even more powerful' again.
I'm sure my players aren't alone in observing there really aren't many feats that spellcaster really and truly desire.
Nod. I'd say it's just fair-is-fair, except feats are /optional/, so if casters are 'balanced' by a lack of desirable feats, they're 'imbalanced' w/o feats available?
What ideas for such feats based on previous edition efforts do you think are suitable for 5E?
Well, the Sorcerer called dibs on meta-magic, so I suppose those are out. Similarly, item crafting doesn't seem like a practical option in the standard game.
In 3e, there were feats, like Combat Casting, that helped casters scrub the few meaningful restrictions they still faced (which isn't much help in 5e as there's only one meaningful restriction left, Concentration), and others that let them pile-on to already out of control aspects like save DCs (which'd be poison to BA).
Sorry, wanting more toys for casters is like wanting welfare for corporations - you'll almost certainly get plenty of it, but you won't get a lot of sympathy when asking for it.