I stopped playing diplomacy. It too easy for TEC to win. Just get more credits and pay your semi private army (pirates) to do your bidding.
The key for TEC are Hosikos with the disable ability, out numbering the pirates 2-3 to 1. Then your turrets, star base, and bombers can keep pounding them. The disable ability also prolongs the battle long enough for reinforcements to matter. Oh yea I like to have 2 repair bays whose AOE overlap the starbase. 60 repair (40 from bay + 20 from Hosiko) is hard to overcome by a disoraganized foe.
TEC also excels on the pirate offensive. Nuke them with 2 Novalith shots. Use Remote sensor to place and time the jump to the pirate base grav well. Use many Marzas with missle barrages, and LRMs with cluster bombs.