I have made IRs of the Kemper imprints and used them with an external IR loader, and the Kones work very well with other modelers in that way. It is the main reason I'd like to see the IR block implemented in the FM3, it would host the Kemper imprint IRs for monitoring. With the proper IRs, the Kones sound outstanding in flat response or imprint mode, better than any other such speaker solution for stage monitoring I've used, especially on loud stages.
Thank you so much for explaining your findings! What do you mean by "IR block implemented in the FM3"? Couldn't you use a second Cab-block for monitoring (at the expense of CPU)? Though as you mentioned an external IR loader: My approach would probably be to throw those Imprint IRs onto my CabM and stick that and my small power amp to the Kabinet. That way, the FM3's CPU wouldn't have to deal with a second Cab block.
Would you mind sharing the IRs you made of the Imprints?