I think there should be more modules,maybe double Resistance modules (Half electric,half physical,or something like that) or half resistance+half armor modules. Since there are modules for cooldown and regeneration,can there maybe be heat and electric capacity modules? Maybe there can also be more legs or torsos with built-in resistances,but not so high HP.

With the next update there will be multi resitance modules which give all 3 resitances.
There will also be resistance kits which give resitances for a single battle.

Both will be very expensive though.

Your idea of double resitance modules is good. I had a similar idea.
But for now there will be only multi resitance modules.