I must admit I forgot the Chiltern sets had power doors. I still expect them to find homes though, hauled by 67's or 68's. They've recently had a multi-million pound refurbishment, they're fully compliant post-2020 and they would be a huge upgrade in comfort over almost any DMU.
Going a bit off topic here, but I suspect DB will be keen to find work for the 67's. Once the ECML thunderbird contract is finished, they won't have any booked duties other than the 2x ATW sets (which may also be going by then if the mk3's aren't upgraded/replaced).
Slightly more on topic, a handful of mk4 sets of 4-5 coaches + DVT would be a much more realistic/affordable way of entering the open access market than a brand new fleet of Pendolinos. Likewise, a 67-hauled version would be a good option for a route off the wires. I wouldn't be surprised to see this, but I wouldn't expect anyone to agree. Nobody seemed to be with me a couple of years back when I suggested new build LHCS as a follow-on to the Caledonian Sleeper order...