It will certainly be feasible to upgrade the basic XTBM to the Pro unit. Most of the mod is adding the switches, resistors, and drilling the appropriate holes in the case. There is also a swap of two traces that I missed on the prototype PCB because that function is not used on the basic XTBM.
I agree that a serial port is in the "nice to have" category. Even though the new PIC includes a serial interface, it takes a fair amount of real estate to provide the actual isolated output. Isolation is necessary because the XTBM ground is referenced to the powerline neutral. I don't think the volume of a Pro unit would justify the effort involved in creating a totally new PCB. And obviously, that would also make an upgrade impossible.
I will place a notice here when (and if) the Pro version becomes available. The main difference is it will include a logging history of perhaps 50 commands. It will also include a separate screen with additional noise information. Right now it keeps track of several different types of noise, but it just displays the dominant number. The Pro version will display them all individually.
Jeff