Well, since it looks like caliber has been decided, next up sights.
I am very partial to tritium sights on defensive weapons. being able to see them in the dark with no reliance of batteries is a major plus for me. Either replace the iron sights with tritium sights (all of my current carry pistols except the J frame), or mount something like the
Reflex sight I have on my AR. (or both if the budget permits).
I've long heard people advocating for Ghost Ring sights on lever actions and shotguns, but have never actually had the chance to try some. Google show that they are made with tritium inserts.
I'm pretty meh on weapons lights attached to the weapon. My experience is that while weapons lights help you find and ID the target, they are not very useful (with my eyes anyway) in picking up standard sights to actually hit the target. Of course, that's for carry or fighting two legged predators. For the situation Jr. Minion found herself in against 4 legged, it might be a benefit.
That said, the House Mossberg 500 does have an mount with a mini-mag light, and with that particular light the bright part of the beam is actually a pretty good aim point at house fighting ranges. I'm just not convinced as to it's usefulness for me on carry pieces / center fire rifles
...even before I read MHI, my response to seeing a poster for the stars of the latest Twilight movies was "I see 2 targets and a collaborator".