Maybe the 'baby Pendo' could be an overhaul e.g. A Class 802, with a revised layout similar to MkIVs, and bigger, taller windows (my big Pendo gripe). Or just get a tilting Traxx loco or similar from Alstom or Siemens, and gear the MkIVs for tilt as they were originally designed.
Non-tilting Baby Pendolinos wouldn't be able to use the EPS125 paths on the Southern WCML and thus would be pretty useless. Although there's lots of talk about them being used for Manchester/Birmingham - Scotland they still need to be able to do runs like Holyhead (attached to a new-build loco) to Euston.
The fact that the Mk4s were designed with a tilt-compatible bodyshell doesn't necessarily make them worth converting once they're 30 years old. They have worked very hard in their time and have repaid their building costs already, so unless the work would allow them to do enough work to earn back the cost of the tilt retrofit it simply isn't worth it. IIRC Mk4s are wired just as normal LHCS rather than being like HST trailers so if all else fails they don't absolutely need to be used on a mainline at 125mph.
When the French converted a TGV to a tilt prototype they didn't bother with the powercar, so I don't think tilting locomotives are necessary (apart from the driver's seat).
