It’s not possible to do that because you’d need to change more than just central Manchester and it would have a huge impact on the rest of the country. Remember, May 18 was a huge upheaval as it was a full timetable recast, and generally, if it worked, did a lot of good (although some will obviously disagree).
Thats why it would need to be slightly modified, however East Midlands, TFW, Avanti and Cross Country run to pretty much the same times as they did pre 2018, so the paths in the North West should still be there if both Transpennine and Northern change back. Paths across the Pennines are still pretty much the same for Hope Valley, and if Calder Valley paths don't quite match up at Leeds then dwell time at Bradford interchange or Brighouse could be extended slightly. Increased acceleration on the new units will probably make pathing easier.
The TPE paths for fast services across the Pennines are pretty much the same as previous so could revert to their new paths and stopping patterns east of Leeds, with Northern taking back the stoppers.
Eastern side Northern that doesn't touch Manchester / Preston could probably remain as it is now, as it is largely independent of the west side, although Halifax to Hull would probably have to be extended to Manchester and not take a separate path between Leeds and Halifax.
There aren't many places in the North West that the proposed B+ timetable benefits over the pre 2018 timetable, Chester to Manchester would lose 1tph, as would Buxton to Manchester, but the Buxton service could easily become an extension of Preston to Hazel Grove in the future if bi-mode stock was ordered or the line electrified, without affecting central Manchester and some of the stations that got increased services such as Gathurst and Meols Cop could retain them again without affecting Manchester.