I was just fiddling around with this question the other day. I think you want to use the Chieftain, not the more expensive Alliance ships:
this build is the best I came up with (ignoring engineering). The other two both have an extra module slot, but in both cases you're either using the second-largest slot for a shield or going shieldless, so you spend more for less agility and not much gain. One nice point for these Alliance ships is that they all have a number of hardpoints on the ship axis, so it's easy to line up the seismic launcher and abrasion blaster shots.
Of course, you
could stuff those military slots with HRPs and go shield-less and probably be fine. An
unshielded Crusader can mine 72T of core (cargo+refinery) with a fighter, a C3 turret, and 1500 armor points before engineering, which should take care of your average NPC pirate threats. That said, if you're truly set on core mining with a fighter bay, you really are going to be better off in a Krait II (gets you 128T cargo, with shields, a fighter bay, and more collectors, plus more C3 hardpoints for weaponry). Ironically, the difference in price between that and the Alliance builds is about one Asp/Chief-load of void opals.