The main issue I see with pirates is that they don't make a ton of sense under the rules of Aurora, you need a source of minerals to build, repair, and maintain ships, a shipyard and/or maintenance for same, a way to pay for it, and a population to man those installations.
I like the idea of sort of having them in an abstracted form like described above, as a sort of passive drain on resources on improperly secured shipping routes, at least from a role-playing perspective but I gotta ask exactly what benefit does it bring to the game? It adds a lot of micromanagement but doesn't bring in a ton of fun I don't think, especially when you can just SM those same consequences yourself.
Since pirates need a base to operate from, that suggests a couple options that might be fun though, let's say, as was mentioned earlier, a civilian corporation wants to get into the more direct acquisition of wealth, we already have a mechanic for them building ships, so having them launch a ship that registers as a freighter until it is feels safe enough to go raiding might be fun, it could hit your civilian shipping, or maybe even that of your allies or other factions. Maybe we could have an additional function of ECM be to penetrate that deception so you can root them out.
Another option is mutiny, currently morale on ships only really matters to military vessels, and even then they can still function with low morale, what if we have ships with low enough morale have a chance to defect to another faction? Say your sentry picket who you forgot about on station for three years gets fed up and decides to rehome to the civ you've been having it keep an eye on, incidentally providing that civ your sensor data or research, or your poor overworked freighter who has been shipping automines from Sol to your newest outpost eight jumps away without a break for sixteen months decides likewise and makes a gift of it's cargo to a (hopefully) grateful new employer? Those could actually be fun and make an impact on the game, while still taking advantage of mechanics that already exist.