Hello Adam,
AZ Controller is based on the same API as Cakewalk ACT MIDI (and all other Cakewalk Control Surface plug-ins). ACT Dynamic Mapping (in many posts referenced as "ACT", while it is just a part of it) is doing exactly what you describe, when you somehow change the focus (by mouse, keyboard or the surface), the mapping is changed to that plug-in. Logically that also introduce a limitation, only one VST can be controlled at any particular time using this Dynamic mapping. The system can be asked to lock the mapping and no longer follow the focus ("ACT Lock").
Within AZ Controller there are several advanced method to focus particular plug-in from the surface, for example it is possible to configure a button to bring particular effect (f.e. EQ) of particular track (f.e. "VOX") into focus.
It is also possible to control some parameters "directly", without ACT Dynamic Mapping. F.e. always control Compressor ratio for "VOX", in parallel with current plug-in in focus.