That depends on where you put the upper limit for the pve bounty missions you want to do.
For ERT a SH won't be enough to kill a Hammerhead, but is enough to farm up to the VHRT missions.
A Connie can handle ERT without issues.
But as all guns now have the same range, ideal balance would be as much DPS as possible with good protection.
That includes Vanguards (though ERT Hammerhead will be hard with them), Ares (if you can aim good^^), 600i...
If your goal is just up to VHRT as the time spent Vs earning ratio is better than doing ERT, then you can use any light fighter, gladius, hornet, sabre, buccaneer...
I personally use the hornet or buccaneer up to VHRT as they have the most DPS of the lights and are still quite agile.
Edit: the upcoming Scorpius might also be something to consider. As a pilot you have access to 4*S3 guns. Of course better with a gunner.