The seawall in Vancouver around Stanley Park is fantastic. I have visited on several occasions, walking the full circumference once..
It would be disingenuous to compare the Riverfront Trail system in greater Moncton to the Seawall, but, if you count both sides of the river, the trail system in Moncton is also well over 20 km in length too.
The vast majority of the Riverfront Trail is (and should remain) a pristine walking and biking trail,
but, there are sections (like along Coverdale Road in Riverview), and, along the downtown riverfront in Moncton which lend themselves well to intensification and commercialization.
For example, the sky has not fallen because of the Holy Whale Brewery and it's patio overlooking the trail in Riverview. The Gateway development in Moncton also will not be an existential threat to the trail (despite what the Gang of 34 says).
The whole length of the downtown trail from Hall's Creek westward to Gateway could be intensified, at least to some degree, of course leaving appropriate green spaces for strollers to enjoy and commune with nature. There should be pathways and look outs built to interact more closely with the riverfront marsh. Space should be left for activities, concerts, special events (buskers, Rib Fest etc), and for monuments and memorials (like the RCMP Memorial). At the same time, a number of options should be created for riverfront facing restaurants, snack shops, pubs, and tourism related retail space.
I think one interesting possibility would be to reserve space for a Museum of Modern Art along the riverfront. I know that the city has been toying with this idea as part of the Ashford/Downing development. What if it was placed across the street where the old fire station is? Just a thought.
Imagine an expansive second floor viewing space in the gallery with windows and a large patio overlooking the river (and the tidal bore). I think it would be fantastically popular.