Even if you don't unlock a tractor unit as a bonus type, you'll have riot starships and good odds of finding a mark V spire tractor platform fabricator. Here are a few ideas for offensive use.
AI has a moderately defended system with zenith bombards? They can be a pain to chase down, so don't. Optional: Pop your entire fleet in, free all the system defenders, pull back through the wormhole. They'll all cluster up on the wormhole. Next, making sure your guys are still on the wormhole and not traveling to a rally post, send the fighters in first, wait a moment, then send in the riot starships and the rest of your fleet. The Riot Starships should lock down those pesky zenith bombards so you can kill them without a pesky chase. If the enemy system is strong enough, you might keep your forces small enough (firepower comparison I -think-) that they don't pull everything off guard duty.
The higher mark riot starships will unlock paralysis tazers, which can help soften the initial attrition on entering a system - I still always lead with fighters, however.
MkV spire tractor platforms are very, very good at dealing with threatballs. Unfortunately, queing up the movements on the galaxy view results in travel too fast for the tractors to kick in. So you'll send the tractors in, preferably with a cheap screen, then wait a moment and pull them back to your defenses through the wormhole. It gets frustrating sometimes, however since you can't let your focus waver and it definitely gets harder the more important it is to soften up the threatball.