So for the PHB itself I just want the artificer. It's established in 5e. It has a solid theme and class story. And it has unique mechanics. It works well as a half caster due to that leaving space in the power budget to have impactful subclasses, which all completely change how the class plays. Putting it in the PHB would ensure that it's supported throughout ODnD rather than being forgotten as an afterthought like the 5e artificer.
For a gish/duskblade/magus/swordmage/witcher class, that doesn't need to be a half caster in my mind (though it could be a half caster), and shouldn't be in the PHB. It has no history in 5e, and so would probably need more time to bake via playtests. It lacks any class story at all currently which is probably one of the reasons it's never stuck throughout editions. Giving it a class story such as witcher would actually give it a concept to build around. Maybe with subclasses based on different creature types which it hunts.
Mechanically its signature ability should be inflicting magical effects and elemental damage via weapon strikes. But how it does this could differ wildly depending on the implementation. It could function like the old spellstrike mechanic, but with how spells work in 5e/ODnD that would probably be messy. It could get a nice selection of blade cantrips, but cantrips don't make a class ability. It could get a good selection of spells like searing smite and ensnaring strike. It has the same problem as the bladetrips, but at least the spell level varies.
It could even be not a caster at all, and use strikes like the arcane archer uses shots. Picking them up like a warlock picks up invocations.