Honestly, if you start a balance discussion with "This item is fine because I need it to solo a group of 4+ enemy ships who are all larger/more combat oriented than me", you've already kind of lost. I don't think it's possible to design a module that can let you solo multiple top-tier combat ships without completely breaking PvP when that module is equipped by said top-tier combat ship.
When you're running solo, part of the challenge is that you just have one ship. There's only so much you can do with one ship. That's okay. Know your limits, and don't bite off more than you can chew. If you want to take on something bigger than your ship can handle on its own but you don't want to go into Open to do it, grab a friend and go into Private. Otherwise, keep in mind that the game won't do anything to keep you from trying to solo a Farragut, but trying to do so is probably a bad idea. If you know you're getting more attention than your ship can handle then go 3/3/0, hit your turbo, turn off flight assist, and start charging your FSD. Most NPCs don't know how to keep up with someone who's coasting at turbo speed (though this is much easier in faster ships).
I run in a Viper. I know I can't take two ships at once without some backup because it's a Viper. I know that I can't take a Python or Anaconda unless it's distracted or already in bad shape. I don't run SCBs, but I've only died in it once, when a large ships caught me off guard with a boost and I went splat on its windshield. Instant death by ramming aside, surviving in Solo is pretty easy if you just know when to hold 'em, and know when to NOPE.
Having an equipment slot that removes the need to NOPE out of bad situations is just being lazy.
