A little off the subject, but one of the advantages of the 9mm,40, and 45 over say the 38 special and 357 is the OAL of the cartridge. The shorter ones are obviously easier to load in a revolver than the longer 38s and 357s. The moonclips also have the advantage of clearance over the bulkier speedloaders. What if you didn't have the problem of BOTH long cartridges and a bulky speedloader? Mmmmmmm....
I tried a little experiment and trimmed a bunch of 38 special cases down to the length of a 38 Super Auto. 9mm length seems to be a bit too short for the speedloaders. I then loaded them as if they were a 9mm with my usual 9mm/38 Super powder. I was using 124gr fmj bullets. They were quicker to load with speedloaders, extracted quicker with less chance of hanging up on the extractor or grips, and shot as well as my regular 38 spec loads.
The disadvantage is that they would be harder find on the ground if at a match since their size causes them to blend in better with the usual assortment of 9mm, 38 Super, etc on the ground. Plus since you have to spend extra time trimming them to length, you sure don't want to lose anymore than you have to. They not be legal in some competitions since they are now a non-production or wildcat cartridge. Like I said, I just did it as an experiment and have never shot it in a match.