So I decided to try using the B variant of rock cruiser, with plan to have a fire bomb + rockman boarder assault tactic.
Well, first I managed to find a fire beam.
Then I managed to find an ion blast 2.
THEN I bought a teleporter, in sector 3 I think, which went almost completely unused until the boss fight after sector 4, because I found another ion blast 2 in a shop there and bought it.
It turns out, it's a LOT of fun just ioning their shield and weapon, and let the fire beam set their entire ship on fire.
Every... single... room, on fire.
Sometimes I even let the med bay live for as long as I could, while the rest of their ship is burning.
It's a strange sort of lethargic feeling just watching them run around, trying to put out fire and repair thing (I'll let them repair the oxygen, if for no other reason than to keep the fire going). I will have my fire beam on standby for when they put out the fire in one room, just so I can set it on fire again. Didn't even bother teleporting the rockman over there.
I pretty much crew killed every ship that way. Dual ion blast the weapon and shield into oblivion, and leisurely burn the ship down (if they're trying to FTL, alternate ion between weapon and engine while focus on setting the engine on fire).