Some idea and comments:
1.) If it have 132x16 pixel LCD why don't use normal (e.g. 5x7 pixel) alphabet? This right-angled dummy seven segment things seems so ugly, I think...
2.) 15C shape is very good, but, why we need to copy the original? Faceplate arrangement, labels, colors, etc is OK, but the left and right handed gray ends of case made to thinner will be looks so better than the original!
3.) Why don't made it thinner than original?
4.) I don't want to take off battery cover to use RS232. After the 5th use of this function the users will be lost the cover. RS232 port without cover / or plugged with rubber cap the good solution, I think.
5.) Changeable faceplate OR "snap-on" faceplate for USER functions or for program LBLs?
6.) LCD and keyboard backlight?
7.) And my old desire: 1:50 and/or 1:20, 1:100 scales on backplate or on the top side of calculator (for measuring drawings, maps, to made sketches on site...!)
Thanx for reading!