For your wants I would say a high end semi-auto with an 18 inch barrel and extended 7 round magazine. Also you would need interchangeable chokes.
Although it does not meet all your criteria a double barrel lupara has a lot of good features. First of all they are much shorter than an auto or pump with the same length barrel and you can still have a regular stock.
A hammerless one with ejectors would be best but even the old hammer models would do. If it has ejectors it can be reloaded pretty quickly and they are dead reliable. Of course having 8 shots available is a big advantage of the autos but after two shots you probably will not need another.
I’ve moved to the double barrel side ... just finished putting rails on a side-by-side with rabbit ears (old west coach style gun). I also cut 2 inches off the stock and added a thick limbsaver butt with five round cuff. The holo sight I’m mounting to the upper picatinny will be sighted to go with the left barrel, which will be the range barrel for specialty (slugs) rounds. A green laser will mount to the end of the bottom rail, for when hip shooting to ‘repel boarders’ and a clip-on sling ring will finish the mods on the lower rail. Found some six round stripper quicks for 12 gauge, for faster reloading. Widener’s may still have a few of the shotties in stock.