So here is my opinion:
A. Market potential
I have never used the SD9. AFAIK there are pro and cons. I read in our forums from you and others, that the image quality of the SD9 would be slightly better then the SD14 just because there are no microlenses like it is in the SD14 the case.
On the other hand I read also many times, that it is more difficult to achieve good/correct exposure with the Sd9 compared to the SD14. Ebery buyer of an SD9 will consider these 2 points.
Third the SD9 is not available new anymore. Only used on ebay. So this is something which has to be considered by Luis to make the investment financially not a desaster for Luis. Any kind of adapters will have less volume as i.e. SD14 dapters would have.
B. Technical restrictions
Here I have no clou. Luis said:
I can not really imagine this, because I do not know how the SD9 looks internally compared to the SD14. Is there a way to show this in a kind of demonstration/ comparison image how this would look like? I.e. Internal part of SD9 vs. SD14?
Best wishes