Yea welcome to SSP, LiamC.
I really like the outlook of your design. Which software did you use?
Also, I would suggest a folded parclo at Highway 321 (while retaining the roundabouts) to make construction more convenient and cost lower. As for the interchange with Highway 142, IMO we don’t really need to redo it if we are gonna abandon the current alignment altogether. That one should be similar to redesigning TCH Exit 29 at James River so I agree with MonctonRad’s comment.
Lastly, if the town of Oxford is upset with being bypassed, we can just renumber the part of Highway 321 between the new alignment and the town as a 100-series highway.