I suggest mutations (which would probably just be perks). Things that make your character different from other humans. Like double dicks which allows you to double penetrate. But they would also have negative effects like increasing sensitivity, or decreasing a stat.
Also maybe make it so that as long as the accessories dont go in the same place, you can use like 2 or 3. The accessories aren't that major, and if you make it so that they dont stack, it wouldnt be over powered. Or maybe make it so that you can only do it on hard mode, or easy mode