Yes, I am pretty sure that is possible.  You can assign a virtual 'footswitch' within the POD Pro to send a Midi CC or PC message to an external device on whatever channel.  I am not 100% how the Shortboard map's onto those  footswitches but I am pretty sure that at least some of them do.  Perhaps somebody else can explain the relationship between the shortboard footpedals and how they map onto HD Pro ''footpedals'.  I know how it works for a Midi controller but my shortboard knowledge is sketchy.

As for channel change etc .... well you need to make sure that your Amp Gizmo (or other 'Midi Switcher' ... there are a few on the market) can fully control your amp.   It depends on the footpedal cable(s) that your amp requires and you would be well advised to check the amp and Switcher specs to make sure that your amp is fully supported - hint: email the vendor if in dou.  With that confirmed, the HD Pro should be able to send the MIDI commands to the switcher (CC or PC as required by the device, again check documentation)