Interesting use of the SVHS, Jeff. Years ago, I had a similar save on a multicam switching job I directed. It was a truck situation and when I began digitizing the Betacams, learned audio wasn't routed properly at all. In some cases, a slow speed but "H-Fi" VHS for quad split TC window logging wound up having the best audio!
If a missed roll can happen in a narrative situation, have to wonder how often this happens in a chaotic reality/doco bag mix situation.
I assume I'm missing a drawback but..
Wouldn't it make sense to have an established record triggering protocol in pro dual system situations? I mean beyond following time-code start..which won't help in continuous TOD use.
I'm thinking something akin to the wireless (w/hardwired option) sync ports used in flash still photography.
http://www.slrlounge.com/wp-content/uploads/2012/08/Pocket-Wizard-Plus-3-on-Nikon.jpg