My question really is: would you prefer a 25-key melodica with a range shifted a bit upwards? To me, A3-A5 would be ideal.
Yamaha isn’t likely to change the P-25F, but they or someone else could introduce a new model.
One issue is that the keyboard layout would look very odd regarding the black and white key pattern; their current P-25, P-32, P-37 keyboard layouts look like what you’d expect on a keyboard. A shifted keyboard, especially, A3-A5, would probably need the top cover painted to show nonfunctional “phantom keys” just to avoid having unexpected visual distraction.