I think that whenever the I-85 connector is FINALLY completed, this needs to be seriously explored because there's no reason to have an aging freeway running through a fast-growing urban area when there's a brand new interstate a mile away. I am pretty sure that a 147 rebuild is on the horizon given its age, and Durham shouldn't settle for a new freeway like Winston-Salem did.
This would be my preferred alternative. Coming out of the interchange with the I-85 connector, 147 would instead follow the tracks more closely and merge onto Pettigrew St. It would follow Pettigrew up to Fayetteville St, where it would then transition onto Jackie Robinson Dr. At the ATC, 147 would transition back onto the current ROW. At the Chapel Hill St intersection, it would shift over just slightly onto William Vickers Ave before transitioning back onto the existing ROW. As 147 approaches the Duke East Campus, it would transition onto Erwin Rd briefly before reverting back to the current ROW once past the Anderson St intersection. From there, 147 would follow the existing ROW up to US 15/501 at which point it would transition back into a freeway before merging with I-85.
I'm not sure how realistically feasible any of this is, but I think that the section from the I-85 Connector to ATC wouldn't be that difficult, and would allow for construction of the urban boulevard to commence without disrupting very much traffic. Also, rerouting 147 onto Pettigrew/Jackie Robinson would allow for the complete removal of the existing route which would result in normal-sized blocks, instead of tons of roads all parallel to each other within the same block.
Edit - been playing around with this for wayyyyy too long. I decided that extending Morehead St from ATC to Alston Ave by connecting various exit ramps and side streets, then having Morehead follow the existing 147 ROW to the I-85 Connector would be a great way to have a second urban road parallel to Pettigrew. This would allow for the removal of the Freeway, but would avoid creating absolutely massive blocks south of Pettigrew/Jackie Robinson. Both Morehead and Pettigrew would run parallel from ATC to Briggs Ave, at which point both would revert to one-way streets and morph into a freeway. I think that Morehead could be the higher volume route, while Pettigrew/Jackie Robinson could be a lower volume street that is designed primarily for bicyclists and pedestrians. At the ATC, where 147 would rejoin the existing route and carry higher traffic volumes, while bicyclists and pedestrians would be routed along a different parallel road (maybe Main St).
is the link to my map on Google Maps if you want to look at it more closely. (You'll probably see other infrastructure ideas around the Triangle as well that I've toyed with). Not perfect but I think it addresses most of the issues that have been raised about building an urban boulevard.