We simply dont know how the Belle will be run, so speculating on prices etc is pointless - however even if it ends up all 1st class pullman dining and they dont retain any third class seating, it will still generate a vast amount of publicity and interest in a working EMU, with profits going towards the restoration of the rest of their rolling stock and the setting up of a dedicated museum. I can think of worse outcomes...
With regards to the unit itself, i really dont see the problem. If using CIG gear is the only way to get it on the mainline, and its that self-powered EMU selling point which has generated the interest and the investment, then its a sacrifice worth making to keep the units EMU heritage regardless of the need for surgery. The alternative, if you can call it that, is to see either all the vehicles rot until their broken for spares, or have the trailers converted to vacuum braked first class loco-hauled pullman's, quite possibly on new bogies as well, at considerable cost. The DM's (MBPT's) would be lucky to even receive that, given the cost vs limited seating accomadation.
While im no fan of a CIG/BEL hybrid, i think you have to be pragmatic. It will keep the vehicles mainline EMU heritage with as much, or less, modification to the trailers than they would have required for VSOE or preserved line use, while ensuring the DM's (MBPT's) have a future beyond the scrapman; the operation of which will help the trust meet its aims of preserving its other EMU's and the setting up of a dedicated museum.
The loss of 1881 is a different issue. Relatively speaking, there isnt a lack of CIG's but there is a fundemental lack of money and support to put them on the mainline. 5BEL trust aside, the only other avenue is Bruce Knights but because of the rediculous backlash regarding 1881 he unsurprisingly gave up any thoughts of taking on the Lymmy units - the fact that one unit is now to be used as glorified LHCS and the other is still sitting in Bournemouth Depot says it all. Not for the first time in railway preservation, a lot of blame can be put on counter-productive infighting.
Chris