If you loved the layout of AX8 and DON'T USE Axe Fx III AND FC6/12, then I'd say stay for now, since you're holding onto FC features that even Axe Fx II couldn't do with MFC, like the hold X/Y or control switches. I call AX8, the Axe Fx 2.5 Lite.
But the FM3 is the perfect companion to a Axe Fx III + FC6/12 that AX8 never was to the Axe Fx II. I share FC's with my Axe Fx III and FM3 in a Pelican case that fits FC 12 + FC6. I'm a multi-instrumentalist, so I used to use Axe II and AX8 for guitar and steel guitar. Now with multiple inputs and outputs, I use less gear! If I'm doing a gig with just FM3 and guitar, I can use the same case, because FC6 and FM3 are the same size! I play both in situations where my gear is in cartage (trucks and rolling racks) and when I'm just a dude with a Honda Fit LOL