After googling "Axe Fx 3 amp in the room" this thread was the top result.
I tried the Filter block trick (no add. EQ) and it sounded amazing through my 1x12 FR cabs. My sound was brought to life and not weighted down with coloration of an IR.
When I tried through my Mackie HR624 monitors, the sound was too crispy and crunchy but a little EQ fixed the sound though.
This method got me thinking about mimicking actual speakers. I've been experimenting with the Filter block and adding either a GEQ and/or PEQ and tweaking the freq's to try and represent the response curves from Celestion. This way, any additional outboard gear is omitted from the signal chain that would normally be within an IR. I also realize that this may only end with "ballpark" results but all in all, it seems much more organic and the "amp in the room" vibe is instant.
From one rabbit hole to the next.
A couple things to note: The response curves they publish are on an infinite baffle (a physically impossible but theoretically helpful setup to remove factors like the size and shape of the cab from a comparison of pure speaker designs). What this means for you is that just setting up your EQ curve to match the posted frequency response won't match that speaker inside a cabinet, just that speaker mounted to a theoretical infinite plain, or mounting it directly in a large wall rather than inside a cabinet.
Another is that your FRFR speakers won't quite replicate the way a guitar speaker is directional since they're designed to sound even despite where you're sitting. Guitar speakers roll off a lot of highs when you're off-axis, and that you won't quite be able to get right.
But by all means, simulating a speaker instead of a close Mic'd speaker is a pretty justifiable goal, since the mic (or reverse speaker if you will) changes the sound quite a bit itself.