TheCosmicKid
Hero
It's pretty seamless to swap a class from standard spellcasting to warlock-style casting. They progress through the spell levels at the same rate, and neither offers blatantly more power than the other. Some people object to making healing magic available on short rest, but that's already possible with the multiclassing rules (and fighters can always heal themselves on a short rest) so I don't buy the objection.Alternatively, I wouldn't mind a spellcasting Bard as much if their spell slots worked more like Warlock's. Always casting at the highest level, few spell slots, refreshes on a short rest.