I've always held that, of all operators, XC are the ones who would benefit most from bi-modal 80x's due to our nation's patchwork electrification.
Hear hear! As I said, any train is better than no train! Regarding your 153 proposal, that's not as mad as it might sound. The 170s that XC runs are capable of working in multiple with 153s, iirc.
Regarding the Mk5A's, I seem to recall a bunch of Class 67s in storage; iirc, they
are cleared for 125mph (correct me if I'm wrong?), so it might not be
entirely out of the question to run Class 67s with a rake of coaches as a stopgap? Unless the couplers aren't compatible?