Yeah I'd keep the arcane tricker and eldritch knights under their current parent classes. They each are there just to give a tiny bit of magic and infuse magic into the class's main gimmick (their and attacking respectively)
The Gish class to me be magic and martial intwinned.
Again my personal idea would be burning spell slots to add riders to attacks. Different weren't subclasses would have bonus riders.
- Fire- Fire damage plus AOE Knockback
- Ice- Cold Damage plus immobilize then slow
- Lightning- Lightning damage plus daze and disarm
- Thunder- Thunder damage plus deafened and knockback (Duskblade only)
- Acid- Acid damage plus Attack disadvantage (Duskblade only)
- Vampiric- Necrotic damage plus HP drain (Duskblade and Death knight only)
- Ghoulish- Necrotic damage plus paralyzed (Death knight only)
- Poison - High poison damage (Death knight only)
- Ghostly- Necrotic Damage plus frightened (death knight)
- Dragon breath- Fire Damage AOE cone (dragonfire)
- Dragon Fear- Psychic damage plus frightened (dragonfire)
- Dragon Wings- Bludgeoning plus launcher into AIRCOMBOOOOOO
gishes should be able to air combo it's the only class that makes sense doing it.