I just tried it. Pretty nice.

With just a bit more effort your batch mode could create a CCF file instead of a .hex file. That would be more convenient for most users.

I just tested Hex2CCF and was a bit surprised to discover only its panel numbering is limited to the 0 based system used by IrPanels. Its button numbering follows the .hex file.

So if your install instructions also requested the program hex2ccf.exe, your batch mode could issue the command
hex2ccf filename.hex filename.ccf
and get a CCF file with properly named buttons (inside unfortunately incorrectly named panels if the first function number isn't zero).

For users who are used to GUI's, it saves a lot of effort to not need to
1) open up a command prompt
2) cd to the correct directory
3) type that command.

Also, some of the Denon PDF files (such as AVR4306_AVC4320_remote_codes_list.pdf) include the function numbers in decimal. So it would help if your program had the option to type in the number in decimal instead of backwards binary.

I'm not sure (since the PDF I have doesn't show any nonzero values in bits 39, 40). But I expect when Denon shows that decimal number it only covers bits 29 to 38. So you might want to call it "Decimal Data" rather than "Decimal Function" and your program would still need to add the contribution of bits 39 and 40.

That would also require a paragraph in your documentation to explain that the number Denon puts in the column named "No." in some PDF files can be used in place of the binary data bits 29 through 38 (to save the user a lot of typing).

You're probably a better GUI designer than I am. But in case you like it, the way I'd change your GUI would be to add space above the "Data" label and below the "Copy to Clipboard" with an I/O field and a checkbox for decimal data. With the box checked the decimal data is input and the backward binary data output. Wity the box unchecked vice versa.