Levistus's_Leviathan
5e Freelancer
They tried a Gish Wizard subclass, it's called the Bladesinger, and it has major problems. A true gish would be a half-caster.A wizard sublaclass.
A sorcerer subclass. Though a monk subclass could also work.
Most definitely a druid subclass.
A fighter subclass.
Psionics =/= Spellcasting. That's all I have to say, psionics does not work if it is based off of a sorcerer subclass (Unfortunately, WotC doesn't agree with me).
Except limiting a shaman to a druid subclass limits character design potential.
They've tried to make fighters that can support their allies (Purple Dragon Knight, some Battle Master Maneuvers), it doesn't work out too well.