How many divine themed classes to we have?
All clerics, celestial warlock, divine soul sorcerer, zealot barbarian, paladin. Then you have the alcolye background for minor religious flavor.
I think that if we can find room for all those we can find room for a fighter that can cast spells arcane spells better than the eldritch knight and worse than the wizard and without the warlock baggage.
Again, literally describing the Artificer...
Though thinking on it, the conceptual space I could see a Swordmage (or whatever you want to call it: the main problem here is the lack of a traditional archetype with a convenient name) filling would be that of a two-thirds caster: not sure if that would work, but the slot is there to fill.
Not really. Artificer is an even different focus of arcane power than what I proposed.
Interesting - I see the swordmage as a half caster
Then what would be the difference from an Artificer or Paladin?
The paladin is divine. The artificer is about tinkering with magic item creation. He's not really what you consider to be a swordmage.