To both of the above...
I am pretty sure Fundy Quay will have commercial space facing Harbour Passage. Not sure about the first building but the second will. The Market Square restaurants will open up directly onto it too, now. Or like 50 feet from it.
The lack of business activity along it is partially geography, right? From Long Wharf to Ocean Steel it basically weaves along the water below an arterial. Any future Long Wharf development will likely include moving the path to along the perimeter of the site and away from the tracks, like at Fundy Quay.
Not sure about the connection point. The outdoor rink, skate park, Harbour Station, and maybe the bus terminal/fantasy land train terminal, would all be excellent things for the trail to tie together. But after that, along City Road for half a kilometre, it's desolate. Then again, that's better than going 600m down Crown and then another 800m along an overpass. I thought the original plan was to use Marsh Creek? Maybe that was an ACAP idea only.
Were you thinking Stanley>Wright>Gooderich>Mount Pleasant, or Stanley>Wright>Gooderich>Seely>through the Public Gardens? I'm partial to the latter, the Public Gardens should be more visible and the gradient is more typical of the path.
Lastly, I was just over in that area the other day and it's looking a lot nicer than I remember. Slept-on neighbourhood. The city should work with the province on fixing the Winter St ramps and making it a more typical highway set up. A doodle I made last year would restore the old Winter alignment, signalize the Rockland/Winter/Paradise/on-ramp intersection, and open up some commercial space in a high-vis area:
https://imgur.com/a/uNMwOvi