Well I won the thing with a Red-Tail, unknown gear layout with 3 mantis and 1 rock as boarders and at least 2 heavy lasers mark 2 (i remember firing them in sync, think i also had some sort of burst laser).
1. Beam my elite team (dual mantis, one of them the legendary Mantis thief KazaaakplethKilik

) into missile bay.
2. Beam my vet team (mantis-rock) into ion cannon.
3. Take the fire while waiting for the first team to do something. I think. Note that during the entire fight, you must pause the game whenever the mothership fires the missiles (or later ion cannons, also note that I'm assuming a build including level 2 stealth or better and a quad shield)
4. Beam the elites out and into the laser cannon.
5. Beam the vets into the beam array.
6. Once all weapons are toast, use a quick burst (always make sure your heavy lasers fire AFTER the last shot of the light lasers, and make sure all guns are charged and ready, half-volleys like the AI tends to do won't work) against their shield generator, giving you some time to take out their cloak.
7. Blow their cloak out.
8. Wait until an appropriate amount of the mothership's crew is in the cloaking room (and door room if possible), open fire at the cloak.
9. Enjoy the sight of having killed from 3 to 5 of the crew.
10. Repair your ship and jump to the next battle.
This one was a bit trickier due to the drones, but the stealth should take care of the power surges. Make sure you only trigger them once they start shooting, not when you receive the warning. Otherwise you've wasted most of your stealth for nothing.
1. Beam elites into missile bay.
2. Beam vets into laser cannons.
3. Use controlled bursts to take the drone controls out as soon as you can - preferably between steps 1 and 2, possibly sooner.
4. Beam elites into beam array.
5. Beam vets out, if desired you may attempt to grab some attention to keep the drone controls offline.
6. Once beam array is offline, destroy ship by firing at drone controls. WARNING: Make sure that all but 1 of the mothership's crew are dead (got lucky by starting a fire in the drone bay, kept them offline for the duration of the battle) by luring any survivors into the drone control room. Failure to do so will result in the following:
A: Mothership will become an AI. Presumably very bad, but I haven't experienced it.
B: You will have left some of them alive, forcing you to deal with boarders in stage 3. Assuming you did stage 1 properly, that's not necessarily a bad thing as it lets your boarding teams do something productive after destroying the weapons, which you may be able to knock out without them.
7. Fix up, jump to stage 3.
This is a cakewalk if you did the previous stages right. Just keep the shields offline and watch for that power surge.
1. Take out zoltan shield.
2a. Beam elites into missile bay, beam vets into laser cannon.
2b. Fire all weapons at the enemy weapon systems, emphasis on destroying missile launchers.
3. Disable enemy shield generator. This will allow you to deal damage without having to time your volleys efficiently.
4. Well, blow them up already! Note that if the mothership should do a power surge, your only escape is to cloak. As in stage 2, wait until it actually gets into the "I'll deal some damage if you don't cloak RIGHT NOW" phase, or in other words, fires the barrage.
5. Enjoy!
Oh, by the way, 2b is more likely to work if you failed to get rid of all (except 1) of the enemy crew.