Cry havoc! And let slip the pigs of war!
Frankly, I would really welcome optional rules for spellcasting as well as survival aspects of the game.I feel like there's enough room, even in the current 5e class composition, for spellcasting structures that allow for multiple preferences.
There can definitely be a class or classes with no cantrips, instead using a few high potency spells. Likewise, there can be a class or classes that only use cantrips and/or low level spells, but gets many or unlimited uses of them.
My concern is that there are so many possible permutations of casting methods, just even the ones mentioned in this thread, that I don't think a single Player's Handbook could contain them all. We've got suggestions ranging from AD&D style individual slot preparation all the way to "cantrips and invocations" style of 3e/5e warlocks.
I would love a dmg that has groupings of suggested options for different game styles. I know there are some now but would like more of them and more recommendations.
I would like an old style with my game with pals and something more current for my kids/family.