So, I know that it's going to be a while before the Cogswell Interchange comes down, and that this thread is a bit stale, but here's an idea of how I would realign the Cogswell Interchange and a few other routes in the downtown's north end:
1. Reunify Barrington Street.
2. Merge Hollis and Lower Water to form Upper Water, and realign it to line up with an extended Cunard St.
3. Extend Cunard to Barrington, bisecting the St Patrick's Alexandra site just north of the St Patrick's building. This route will require the relocation of a few heritage buildings on Brunswick and the demolition of a few buildings on Gottingen.
4. Extend Cogswell past Barrington to terminate at Upper Water.
5. Introduce 2 new local roads each north and south of Cogswell linking Barrington and Upper Water.
6. Link Rainnie Dr to Trollope a block south of the Cogswell & North Park/Ahern intersection to eliminate the 6 point intersection.
Just a few ideas that I feel could improve traffic flow and create some new development and/or park land. Perhaps a bit far-fetched, but why not shoot for the stars?!