I appreciate things change over 30 years, but the investment submission for Networker Turbos for Thames Valley services went to BR's Investment Committee at the same time as the BR/NSE Crossrail proposal was being developed; this resulted in the Committee asking what would happen to the Turbos if Crossrail went ahead. Paraphrasing the reply, it was something like "no problem - the Turbos can be converted to EMUs"; I don't think the reply gave any detail, but from what I remember the wording was such that it implied this it would be a relatively easy task. But certainly, the possibility of converting Turbos to EMUs at some future date was considered before the trains were procured, and presumably this would have been reflected in the specification. Consequently, mixing Turbo's and 465s together might not be too difficult, but I don't know if there are any significant differences between 465s and 365s.
Regarding Magtec, most (all?) of Optare's battery buses use that company's equipment, and they have developed battery/electric propulsion packs which can be substituted for diesel ones in existing fleets; films of some of these can be found on YouTube. So as first generation DMUs used bus engines/etc typical of the mid/late 1950s, could the 165 HyDrive project also "pinch" proven bus technology? Moreover, my understanding of the Magtec system is that it could link into the existing Gmeinder final drive.
Regarding references earlier in the thread to branch lines, the 'Modern Railways' article also states that the GWR Turbos will be refreshed internally "with improved interiors better suited for long distance services"; doesn't that imply that they won't be operating branch line services?