Play Cmdr Cheyd's "IronMan" type game: If you get killed, you delete your commander file and start again from Lave and 100Cr. That should boost difficulty to a pretty notable level.
Actually, when I do play (very rare) instead of do OXP-work these days, I have been playing "Broke Iron Adder" games.
0 Cr
0 Missiles
0 Fuel
In an Adder.
Delete the commander and start over at that if you die.
My best pilot has an ECM, LCB for a total of 5T, Fuel Injectors, and some cash. And a whooping 4 kills IIRC.