There's very, VERY little room to expand the Water Gardens, but why not make that VERY little count?
At the Lancaster edge of the park, there's nothing there but a blank wall and some grass in between it and the sidewalk. It's not appealing at all.
How about expanding it to where there's a 7' water wall/bench/art piece to cap it off? Not stopping there, I would plan to have Water Gardens Place expand on its own, while being integrated into park which would more than help the pedestrian level of that place, especially on the Commerce side. The building would become an urban aquarium and the top floor would be a restaurant. Four of those six long strips in the middle with arches on top could be designed to feature 4 water falls cascading into pool. That pool could feature a living, active water sculpture from Bing Thom. Maybe like a water tornado or something like that.
Back view of Water Gardens Aquarium