While playing in skirmish mode you can capture Merchant Space Docks which can be a very good way to supplement your forces regardless of which faction you control.
IPV-1 Patrol Craft
This beauty of a unit is essentially a Tartan Cruiser that costs 100 credits less. It comes with shields and the same ability to boost its cannons that the Tartan Cruiser has. It has slightly less hit points but can fill the same role as a Tartan cruiser easily and more cheaply.
Pirate Fighter
This fighter is a nice middle ground between the TIE Fighter and the X Wing Squadrons. It has no shields like the TIE however, a Squadron of pirate fighters can take far more damage than a TIE Squadron. They are slightly more expensive than TIEs and slightly less so than X-Wings. A good supplement to any attacking force.
Pirate Interceptor
Another mid range capital ship from the Pirate units. This Frigate can boost its cannons like an Imperial Acclamator and in addition is capable of taking a significant amount of damage. They arean excellent addition to a front line attacking force due to their hardiness and ability to hand out damage. Use them as a screen for your cruisers and the Acclamators and Victorys can pump out fighter and bomber support at will behind the Interceptor Screen.