Hi mykrobinson,
It is possible to achieve what you're describing, albeit with an extra track for routing. It looks more complicated than it is...
Here's the example setup:
1. Create 3 source vocal tracks: Vox 1, Vox 2, Vox 3
1.1 Add any sends from the source vox tracks to effects etc.
2. Create a Vox Folder track as a parent folder to the 3 source vocals: Vox Folder
3, Create a "Vox Buss" track to route the vocal audio to/through
4. Turn off the Master send on the three Vox source tracks so they don't send to the parent folder.
5. Create sends from each of the vocal tracks to the Vox Buss track.
6. Add Vox Folder as a VCA Lead on the Track Group of your choice
7. Set the 3 Vox source tracks as VCA Follows on the same Track Group.
Now the folder track fader acts as a VCA to the Vox source tracks, keeping the relative send ratios etc.
The audio doesn't pass through the folder track but instead heads to the buss track.
It took way longer to type all that than it took to do it in REAPER.
Hope that helps.
Here are some images of what I mean...
(In case anyone wonders, the I'm using theme is Commala 5)