A serco test train is good for exploring routes that have lots of ends. And loco haulage to places where you wouldn't normally see it. True to real life.
Oh I have no doubt that there will be enough interest - trouble is people will happily sit back until they are able to download them and not actually say anything so you don't know if what you are doing is good, bad or indifferent. If you really want comments, you could try and outlandish 47 or 73 repaint
You could wait a while to upload them, as James Hunt is making a new version of the Mk2/3 sets with transparent windows and interiors. I think it looks great though!