It'd be nice if the Ion Thruster part was customizable like the other chemical/nuclear engine parts. I'm thinking that the customization choices for the thruster could be the following:
Engine type: Electrostatic [Gridded, Hall effect], or Electromagnetic [VASIMR, Magnetoplasmadynamic]
Propellant: Xenon, Hydrogen, Krypton, or Argon
Power input: Solar, or Nuclear (along with customizable voltage slider)
Here are some IRL engine tech demonstrators that the in-game engine specs can be based off of:
NEXT, VASIMR, MPDT, HiPEP, DS4G, LiLFA, NSTAR, and PPS-1350.
thx bud. @yopo