It’s not that bad, the C comes with 16+5 slots, an S would come with a bit extra. That’s enough for a light fighter. You need the 5 base slots (though hyperdrive is optional, and I haven’t checked if the photon cannon is now removable yet), one maxed out weapon + rocket launcher (6 slots), 4 slots to max shields, 4 slots to max the engine, and then you have a bit of spare room for shield batteries and other assorted things, though you can also use your suit for that in a pinch.
It’s all a bit pointless, of course, because I haven’t yet come across a pirate encounter that I couldn’t handle with just the basic shield and photon cannon, even though I had a 4-on-1 encounter once. The only thing you need upgraded weapons for are high-level bounty missions, or Sentinels if you’re into that.