I think its rather unfair to say the Arnold Brighton belle was unsuccessful given there is demand for another run. Yes the blue grey one was discounted but so are many other "successful" models. They need to expand on it with something like a 2BIL if anything.
Yes there's the classic argument that there is no demand for 3rd rail stock as the one unit available was discounted. But the same thing happened with the 00 4CEP. Then came a couple of other units, then Hornby joined the party. Now there is a thriving 3rd rail scene in 00. That's a fact. If Bachmann shrunk the 2EPB I'm sure they would sell as many units as the 4CEP at least, probably more given the shorter length.
Minitrix (british models) were around for years, I don't think that can be classed as unsuccessful, more they lost interest and discontinued it. There are MANY locomotives and items of stock available second hand so they most of sold a fair few!
DJM, Well that had nothing to do with N. Plenty of interest in the class 17 and other projects that went for a burton.
Hatton's and KR... Well... Had they announced something like a standard 4MT 4-6-0 or something first then I'm sure orders would be more favorable. Best go for something that would compliment existing stock more widely first I would think. Like the Sonic 56xx. I'm all for exotic locomotives! I just don't think If I was starting a new venture in N I would stake my future on a Bulleid Leader to begin with...