EzekielRaiden
Follower of the Way
Not to take over the thread with "How Ezekiel would do classes that don't currently exist," but my approaches would be:I think multi classing is a fine concept, but I don't think it's current incarnation is that great and I would rather have a different feeling one that doesn't mess with level scaling.
Oh yeah! I'm REALLY not a fan of the Eldritch Knight and it's 'Sword in one hand, cantrip in the other'. They should be doing both at the same time!
It doesn't help that a lot of Ranger 'spells' are basically just stuff like traps or 'shoot a lot' because making new spells is easy I guess.
I think Paladins should get 'Miracles' and can spend those 'Miracles' on stuff like smites or a series of utility spells. Basically reverse the current paradigm where you sacrifice spells for smites: you sacrifice smites for spells. It would feel more thematically appropriate and DIFFERENT from the Cleric.
Bard, Cleric, Druid, Sorcerer, Warlock, and Wizard are the classes defined by spells. Warlock has its special wrinkles, the others are about spells pretty centrally, with most other mechanics being fun addenda to the spellcasting. So...lean into that. Make the full casters distinctive via their spells.
Artificer I'm genuinely on the fence about. I think they work okay as spellcasters, but I long for something more built around abilities, yet I understand that such a rework could be dicey.
Paladin: Auras and Litanies. "Miracles" feel too priestly. But a litany--a rehearsed prayer/procession--feels right for a pious warrior who stands strong when the darkness rises, and who acts as a beacon and standard for the faithful to rally around. Auras give passive buffs, while Litanies would be active effects, possibly with call-and-response stuff for allies to take advantage of. I could see a "Knight Hospitaler" subclass getting a Litany for the Martyrs, which lets allies take a bonus action to heal themselves or the like.
Swordmage: Already discussed.
Ranger: I don't know the full details of Level Up's methods, but what I've heard sounds promising. Wilderness knacks and primal/sacred ritual. More or less, the way I see it, Druids bring primal power into themselves to the point that it changes their forms, Barbarians let primal power enhance their natural strength, Shamans invite the primal power to speak for and defend itself. Rangers, then, are where ordinary folk intersect with primal power. So stuff that captures the ways that regular old people would connect to and relate with the beautiful and terrible powers of the spirits-in-all-things would be ideal. Propitiation, reconciliation, exhortation, directed at the natural world and its bounties and violence.
Psion: Whole other topic, might touch on that some day but not today. Just...it shouldn't be spells. It may be like spells, but psionic powers should work differently.
Summoner: Spoilers redacted! I have a work-in-progress that I may someday present on here. We'll see.

Yeah, I've heard of VMC. It's...I appreciate the idea, but it costs so much and gives relatively little. I would need to examine it further to really know if it's worthwhile.Here is one way that Pathfinder 1st edition handled multiclassing: Character Advancement – d20PFSRD As you can see, it involves replacing feats at key levels with the class abilities of another class.