As a person with limited understanding of how a model is actually developed, some of the comments explaining the process and the challenges of getting something from the "it's a good idea" to practical commercial reality is fascinating.
What's equally fascinating is the thrall that this small class, only in service for about nine years holds for so many people. Seems rather similar to the P2 class. I doubt many here ever even saw the P2 in steam. I suspect for a model to sell, and for ketone/djm to make a return, it will need to appeal to collectors, those who buy models because they like them as well as the narrower group that model 1960-65 Western region
Based on previous comments, let's assume the fixed cost of getting a model to market is £100k. If a model retails for £150 of which half is direct cost of production, approx 1300 models need to be sold to pay for the tooling before any profit is made. Now my numbers are almost certainly wrong (I'm not in the industry) but it's simple enough to build up a spreadsheet to show how the numbers vary. However, given the retail price assumption they're probably not a million miles away. Strikes me as a pretty big risk to assume that you're going I sell 2000+ of a class that operated for just nine years. I suspect, though, that part of the business case for kernow is a)brand awareness b) that most people will likely order something else at the same time as their D6xx...
Let's not also forge that if you're investing money, you're foregoing alternative return (the time cost of money). It doesn't grow on trees! If people are serious and want to accelerate time to market, crowd funding could help. However strikes me issue here is not finance but the work / resource/ skilled labour required to get to the production stage