I've been enjoying my 'honey pot' strategy. Have a game where I'm bottled up by a series of heavily reinforced Mk IV worlds with fortresses and the whole works. I have Parasites and Space Planes.
Mk I and II leeches, Mk I and II parasites, tractors, a repair ship, and some other lighter units and turrets (but no Heavy Beam Cannons in range of the wormhole) and I've been getting a decent supply of Mk IV and Core ships even though I don't have an advanced spacedock...