Set the MFC IA to an Block, you be sure, it`s on every preset, like the Amp1 Block. Look into your Axe-Fx, which Controller Number the Axe-Fx "Amp1 X/Y " is set. If you now set THIS Number to any other X/Y Blocks (or all), a hit on the MFC IA will switch ALL Blocks from X to Y, which correspondent to the SAME #CC Number.
Note: The IA Switch on the MFC will only work in MFC "Axe-Fx Mode=ON", if the FX Block, which is set on the MFC to this X/Y IA Switch is also included in the Axe-Fx Preset! So, in our example: If the Amp1 Block would be missed in the preset, but other Blocks with the same #CC as Amp1 will NOT correspondent any longer to the IA, because the IA think: No Amp1 - i`m out ...
That the IA switch do NOT think to be "out" of funtionality, you could set this dedicated IA Switch to "Axe-Fx NONE" instead of AMP1 X/Y. Now the IA would react like a third Party controller will do: As Master who Slaves the Axe-Fx. Now you can programm the #CC Number directly into the MFC and the MFC don`t look any longer, if there is the "right" correspondending FX Block in the preset to sent and receive #CC Number (and therefore X/Y state). In the "Axe-Fx NONE" mode, the MFC sent always the command out. The price for that: The switch in "Master Mode" cannot be slaved by the Axe-Fx any longer: Receive informations about state change when Scenes change (for example) will not longer work.
In short: Yes, you can setup a IA Switch as a "global" X/Y Switch. "global" = all Blocks who are setup to the same #CC Number in the MIDI:CTRL menu of the Axe-Fx - the #number who is prgorammed n the MFC to that switch (or the correspondending fx block x/y)