Those old MTB rigs make nice commuters.
I definitely like drop bars better. I think(?) that one would be easy to change over . . . Something drop, but low drop, like 'Cross bars. Another option would be bullhorn bars which would accommodate your existing levers and stuff. MEasure first, though
The only other things I'd do would be skinnier, road style tires, of which a lot of companies make stuff that will fit. Schwalbe Big Apples for instance, but flat resistant for sure!! A flat on your way into work is really, really an undesirable situation. Spent the money on good tires and look at it like an insurance policy. a few lights and blinkies ( I cheap out and get nice lights at CVS for way less money that bike specific from the shop) and mirror would turn that into a real nice commuter. Maybe fenders later if you re so inclined? In summation, that is the basis for a nice utility rig !