Gotcha, I misunderstood the 3/3 which you rightfully caught as 3/4. Thanks.
The question: "What is the theme?" is the main reason why the Swordmage and the Mystic/Psion don't exist (yet, as separate classes) in 5e.
A class cannot be just a bundle of mechanics. An Artificer is not just a half-caster wizard-rogue. It has a specific theme as a magitechnician, a technosorcerer. Like how the Paladin is not just half-caster Cleric+Fighter; it's an oath-sworn knight empowered to smite their enemies with the power of their conviction, which may or may not be tied to an actual deity like the Cleric but is certainly divine in nature unlike the rousing battle cries of a Purple Dragon Knight (or Banneret).
The Mystic failed because it was a delivery mechanism for a whole host of concepts that were vaguely psionic in nature, not a singular idea. One might compare the Wizard and Cleric as massive classes with massively disparate subclasses, but both classes have very clear core archetypal storytelling concepts they're founded on and just happen to have a huge potential for disparate takes on that story (Yer a Wizard Harry or The Power of My God Compels You).
So what story reason should a class have 2/3 or 3/4 the magic of a Wizard or Cleric? Figure out the story first, not just the combo of this plus that, divided by the difference. In my mind, the Bladesinger is already the 3/4 Wizard, 1/4 Fighter, giving up some of the magical firepower of the other Wizard subclasses to gain some martial abilities that other Wizards lacks. So you have a sliding scale of Bladesinger to Artificer to Eldritch Knight to Rune Knight, and any amount of multiclassing can let you fiddle with the dials to achieve more specific gradations of combination.