I would recommend changing the name of Thor Knights, as it feels really out of place. There's not many Norse references in this game, aside from Fenrir (which is a series staple anyways). Most weapon/character names reference either Arthurian legend (Pelleas, Ragnell, Alondite, Ettard), or Welsh mythology (the exclusive Dawn Brigade weapons). Dark magic in this game also seems to draw influence from France.
My suggestion would be to call them Alchemists. It fits the flavor, and one of their big things is the creation of energy (which makes them fit Thunder). It might make thematic sense to give them things like fire or staves if you did this, but that's not important if it doesn't fit into your design for the class.
Something else that might be cool is changing Tactician/Grandmaster to Cambion/Wizard. In Arthurian legend, Merlin has access to magic because he's a Cambion, a child sired by an incubus and born from a mortal woman. It seems somewhat fitting for Soren/Pelleas, because of the former's mixed lineage and the latter's spirit mark.
Of course, these are all suggestions. Do whatever you want with them; either way, I know that I'm gonna enjoy your finished product based on what I've seen thus far. ^^
On a different topic, I'm really curious to hear about how you plan to balance characters that have poor availability. Since you're focusing on part 1 atm, that would mean Tauroneo, Tormod, Vika, and Muarim.
One last question. I've seen people saying that the demo pretty obviously ends after chapter 1-6-1, and I was wondering if this was because the game crashes? Is it possible to continue playing past this point, although things outside of classes/skills/weapons would obviously be untouched?