Well, it would require the entire street to be dug up so the drainage system could be relocated. Also, it would require variances to a number of the requirements in Chapter 42 with respect to development along major thoroughfares, including building setbacks (zero feet instead of 25), right-of-way width (40 ft instead of 100), curve radius (major thoroughfares require a curve radius of 2000-ft, with 100 ft between reverse curves.
Center roadway infill might be more (physically) practical on low-traffic residential streets, especially ones that have open drainage ditches. For example, here's a street in the Heights with 90+ ft from façade to façade, and maybe gets an average of a car or two per minute, if that. The block face is almost continuous on both sides, with minimal lateral setbacks.
Take the 20 feet closest to the facades on either side and make two one-way woonerf-style streets. Maybe eliminate on-street parking, because people in the Heights hate on-street parking of cars that aren't theirs. That gives you space to lay out townhouses down the center of the RoW, say, 25x50, oriented parallel with the street, in 4-packs so the garages don't take access from the street. Each TH has two external walls, one of which faces a pedestrian-scaled street, and two off-street parking spaces. That's twenty new 3000-sf townhouses: something like $12M of new tax base. On one block. On space that's pretty much going un-used.
All you have to do is convince people that front yards are stupid and a waste of space and not really worth having in the first place.