If someone asked me to recommend the best bang for your buck 12.5-18.5" shotgun build it'd be a tossup:
A 2 3/4" Wingmaster build is hands down better than a Grizzly but its a lot of fuss, which some people dont want to get into.
You need to find an action cheap (many insist on selling the complete gun with a fancy Wingmaster stock and a 28+" plain barrel with a 2 3/4" chamber because they know once separated the stock and barrel will be difficult to sell), then find an ~18" barrel with a 3" chamber, then a stock. Optionally gunsmithing to have it upgraded to a 3" receiver. The price will add up, and you still wont have a short barrel.
As for the whole 'one receiver as a shotgun platform' idea - I disagree with it. When i first got into shotguns I was attracted by the idea of buying one single pump and swapping barrels and stocks for different purposes. But the reality is that often different applications require different stocks, barrels, sights (ghost rings complicate things), mag plugs, etc and and rather than fuss with swapping all that sh*t around you are really better off just buying a second receiver and leaving the guns in their configs.
For example, my hunting shotgun has a full 14.5" LOP stock , a 28" vent rib barrel, standard mag tube (plugged), a limbsaver recoil pad, and currently has some fiber optic turkey sights on it. The only thing that changes on this gun are the sights, so I can pick it up whenever and its already in its optimal config and ready to go.
My 'wildlife defense' gun has a short 12" LOP stock and matching forend, ghost ring sites, receiver/mag tube sling plates, a 12.5" plain barrel, an unplugged mag tube, etc. Unscrewing the rear GR and swapping all that crap off all the time to use a single receiver as a universal platform would be annoying.
The going price for an excellent condition 2 3/4" Wingmaster receiver (w/triggergroup) is around $175. IMHO just pick up a second receiver. You have the option of doing a 3" conversion down the road, or you can just leave it as is: 2 3/4" is all you need for HD/WD type stuff.