is currently designing a 1:450 scale Class 90 electric locomotive. Very much tempted to use the basic CAD model for a 1:120 and 1:87 scale one as well!
The main differences I see are the motors and general size. Though TBH the 90 and 91 should be priced similarly. It may be due to licenses or the fact that two different factories are making them (or possibly three?)
I'm not sure I'd agree with that. Hornby have make models like "The Duke of Gloucester", Cock O' The North" and the Franco-Crosti 9F. All these were limited time or limited range models. So Hornby has the ability to do these types.