Okay, I was unclear about the concept, and other stuff, and I want to clear things up.
I've done about half of a rough draft, on homebrewery. I think the core concepts are clear now, but let me know if I need to explain them better still in the document.
All feature details are up for debate, but the basic concepts represent my mechanical and conceptual goals for the class.
Swordmage rough draft
For the Esoteric Techniques, the list right now is very rushed and way incomplete. The choices are there to represent the sort of things I want it to be able to do, though it's missing conjuration spells. Gonna make a 3rd level technique that conjures lesser elemental critters that do your bidding, I think. Probably using the UA style stat block.
For the Schools. White Lotus is the closest to the classic swordmaster. Guardian is a tanky defender with Aegis Auras. Dervish is an elemental damage focused guy. Hermeticist is the most scholarly Swordmage, maybe gets expanded spell access? I do wonder about a semi-divine School. It would make sense. Get access to cleric rituals, radiant Aegis...could be legs there.
The Aegis is basically a magical fighting style with secondary elements as you level. Your Aegis determines what your bread and butter techniques are. There might be a high level feature or a School that lets you change your Elemental Aegis during a rest.
Absorb Elements, Arcane Parry, and Armor of Agythis, give three low level options to increase your defense at the cost of Aether.