I actually went looking to see if there was a 'law' regarding upper / lower case in Intel Hex files, and the only comment I could find regarding that was on the information page regarding Intel Hex format on San Bergman's site in which one sentence states that the record should be read correctly regardless of case, although he doesn't say where that came from.
I can honestly say that I have never, ever seen an IH file with its alpha characters in lower case but as you say, it only takes a very small change to allow for this rare possibility, so it is a sensible addition.
The problem can probably also be solved by using the Linux TR command to translate all lower case characters in the file to upper case, like this:-(untested)
Code:
tr [:lower:] [:upper:] < originalfilename.hex > modifiedfilename.hex
With regard to the provision of a switch to allow to choose 'New OS' or 'Old OS' mode at runtime, when I originally put it together I couldn't imagine a world where anyone would have more than one MK14 or would need to change that setting more than once... but how little I knew.
We've also discussed the possibility of switches to set the key press / release delay values to optimum for a 4.00MHz machine or a 4.43MHz machine, and for a selectable 'VDU slow mode' which slows down the key entry speed for a machine which is being slowed down by an active, attached VDU. My feeling at the time was that all those options would be better incorporated into a pull down menu on a future GUI version of the uploader.