Check out this recent thread on running 2 amps together:
http://forum.grailtone.com/viewtopic.php?t=17839
I ended up going with the Switchbone for the 2 reasons that it got great reviews and it was intentionally going for a pedal-type option and wanted to get away from rack stuff. BUT, some of the forum uses gave me some great feedback on different types of rack units that are out there. I would agree with the statement that the Mesa HG Amp Switcher lacks features. It would work ok with a Triaxis b/c it has the tip-to-ground switches, but I would really check out some of the other rack stuff out there. The Mesa switcher doesn't have polarity switches or any other controls. I used to have a Mesa switcher and I had mixed sessions with it. With some amp combinations it sounded huge, with others it sounded horrible - and now, in hindsight, I am attributing that to the idea that when it sounded strange the amps were probably out of phase.
Are you looking to switch between the JMP1 and the Triaxis, or are you looking to use them both at the same time? I think that could affect how you set up your effects and power amp(s).