TheDopplerKid Any competent NEXRAD L2 product viewer must certainly have rapid parameter/moment switching with keyboard shortcuts. That's high-level - we will have months to nitpick high-level UI things like this after the initial core releases of areas of functionality (which will not all be on December 13th, because of perfectionism). WSV3 RadarHalo Polyradial Mosaic will be there for release day (the special new technique and service for reflectivity data). The other 5 single-site base moments, probably. Derived L2, probably not until a few weeks later.
The 1, 2, 4, or 8 rapid-switching multimap ability is intended to allow display of diverse data, as well as diverse/independent camera view/map style/timeline state.
So the probe on each map will display the unique parameters you chose, such as different L2 parameters, or any parameters under the probe point like in the V6P experimental first-gen build.
But does this adequately and fully capture what you mean by, "ability to view different radar products within the probe's viewport"?
Possibly, there could be an interlocked inter-map camera view/probe mode where all parameters from all visible map panes contribute to the same rollover text box and all parameter values are duplicated there across maps.
Let me know exactly what's optimal for your radar interrogation workflow.