Riverway Properties’ latest plan for a condo building at the corner of Montrose Blvd. and Marshall St. almost triples the number of units planned for the former site of the River Cafe — from 12 in a proposal aired only a few months ago to 34. But the building’s still set at 7 stories. The embiggening was made possible by expanding the building’s footprint onto a neighboring property (the brick house-turned office to the north) — and switching to an entirely different scheme, from a big-name architecture firm. Philip Johnson, who designed the original campus and many of the buildings for the University of St. Thomas a few blocks away, is not coming back from the dead for this project, but Philip Johnson/Alan Ritchie Architects, the New York firm that still bears his name, has replaced Element Architects as the building’s designers.