For an Enterprise analogue, definitely one of the cruisers. I'd pick the Aegis, since it's got a bit more capability outside of combat, and there's a way to think of it as 'available' (and because I'm more familiar with it). The Cruiser is the more interesting choice, and would definitely work in the role. You might make it out so that after seven centuries half the weapons are broken or something, to justify why it might not be used in a combat role (though it would still be enough to blow every pirate in ten score light years straight to hell).
Problem is, Niops isn't the Federation, so perhaps the Enterprise isn't the right choice. The Vincent and Tracker are both reasonable choices. The Vincent has the cargo to be self sufficient and its a better fighter. The Tracker has dropships, which offer a lot of flexibility that small craft don't, but is worse in a fight and has negligible cargo relative to the Vincent.
There's a sense of being non-threatening with the Tracker or Aquila or Nightwing. To me, that's less of an advantage. Who would be threatened by a Vincent that would also be a threat to a Vincent? What deep periphery power out there has the sort of navy to threaten even a baby warship? Pirates, by contrast, are bullies and would doubtless run like hell from a Vincent, and be more encouraged to pounce on a Tracker. Even leaving aside the information from ISP3, all we know about the deep periphery are nations like the Hansa and Jarnfolk, and isolated colonies like Farstar and Alfkerk. The only likely threat would be a Wolverine colony, but assuming you don't think they ended up on Terra, the threat assessment for them would include a McKenna class warship among others, which would take every mentioned ship all at once (provided it had been maintained for two centuries). So I wouldn't shy away from announcing your might for the most part.
