The GTVA has already captured Shivan cargo, remember the first mission to capture the Knossos portal from the Shivans? There's a bunch of crates with their freighters dropping off stuff.
Besides, SOC only needs to secure a Lilith-class cruiser for LReds and BFReds (by supersizing the technology). Capturing a Moloch will let it have access to intact fighters/bombers within its fighterbays.
Now, to pull off these kinds of operations, they need to have met certain criteria:
-the SOC needs to jam communications in the area so Shivan warships can't call for help (this is doable, since the GTA Hamako jammed NTF comms while you were doing the hijacking of the Sunder)
-have the weaponry to quickly disable and disarm the warship, and take out any fighter wings so they don't escape (also doable, SOC had Erinyes fighters with Kaysers, + Stilletto II's to bust up turrets and engines)
-have the troops and firepower to takeover the ship (I'd say SOC can pull this off too, we know the size and toughness of a Shivan, so the GTVA has had 32 years to develop weapons suited for killing Shivans quickly and efficiently, give these to SOC soldiers and they will wipe the corridors clean of Shivans)
-have some vessel able to haul away the disabled Shivan warship (an Argo transport or a Triton freighter should have sufficient power to carry a Lilith out for sure, might need 2 Tritons for a Moloch)
So you see it's not impossible, and if it's not impossible then SOC will pull it off. After all, SOC is known for doing suicide missions and coming back home successfully