Update: it's amazing what you can learn just by "doing your homework" :^))

Scott (N3FJP) has in fact already implemented an "almost as good" feature for sending CW over the CAT connection to the Elecraft rigs (and others that support a similar feature, like the Icom 7600 and 7610)

In the CW transmit settings, if the function key stored messages are prefixed with "RI:" then the characters that follow will be sent over the active CAT link as command(s) rather than used as text to key the transmitter over a separate keying link.

See the Elecraft KIO2 programmer's reference, page 9:
<https://ftp.elecraft.com/K2/Manuals%20Downloads/KIO2%20Pgmrs%20Ref%20rev%20E.pdf>

and N3FJP's CW transmit settings instructions (quoted below):
".....
With version 1.1, I have added the ability to play saved CW strings stored in your rig (for rigs equipped with this feature). To send a command to your rig instead of sending the string, precede the text with RI:. For example, when placed in an F key string, the following will trigger the Icom 7300 and Icom 7610 internally recorded voice messages: (you must have rig interface enabled and be connected by a com port)......"

For example, if the F4 key is loaded with "RI:SW16;SW08;" then pressing the F4 key will send the message stored in the K2's message memory #1.
the SW16; simulates a tap of the MSG button, and the SW08; simulates tapping the "1" button.

In like manner...
"RI:SW16;SW09;" sends memory #2, "RI:SW16;SW10;" sends #3 and so on.

So in one swell foop [sic] I've almost obsoleted my wired USB keying interface LOL and designated the wireless BlueTooth CAT link as a the keying interface.

What is lost in the scheme is the ability to auto-insert callsigns, serial numbers, etc into a stored message. So Scott still owes us some midnight oil... Break's Over, Scott!! LOL

Jim, N5IB