As you have correctly mentioned at the beginning, WAI is just an indicator. So, with that in mind:
1) can be implemented inside Sonar. In case Control Surface plug-in does not change its location on load.
2) there is a trick:
a) unset "Keep track/console visibility in sync" option,
b) in the Control Surfaces property, select "Control Strips Visible in": "Console View".
c) hide some track in Console view.
Your Track view has "WAI gaps" now and Control Surface only "see" not hidden in console tracks. You still can see and operate all tracks in the Tracks view.
For "Folders", you can select "... Visible in" "Track View". Once the folder is closed, tracks in the folder are excluded from WAI.
It is possible to hide MIDI tracks in the "Track View", but I normally prefer to see MIDI clips...
Warning: there are some bugs when using that approach. In WAI indication, Track Inspector, etc. But there are more for "bug report" and not for "feature request".