[Kevin Sevcik]

Ditto on our team never or very rarely losing a Victor. But as noted, this isn't legal for at least one very good reason. When a Victor is in brake mode instead of coast mode, it quite literally shorts the leads of the motor together so the motor goes into regenerative braking. So if your spare victor or failed victor is in braking mode, you'll rapidly have two failed victors. And if you make a mistake on whether one is broken and start up the second and they're not perfectly in sync, you could end up with current shorting from one to the other as their duty cycles don't sync up.

EDIT: You won't be able to use spikes like this. Spikes are solid-state "relays" not actual physical relays. So they take a constant 12V and GND on the input side that they need all the time at that polarity to operate properly. Then they just send 12V or GND to M+ and M- as dictated by the digital inputs. If you send a Victor output that isn't full on foward to a spike you'll just make it work weird and jitter if at all, if you're sending voltage in the forward sense. In the backwards sense, you'll probably just fry the poor thing. And wiring in physical relays instead won't be legal either.
In summary, the FIRST wiring rules are there for a reason, and it's almost always to protect your team's significant investment in IFI products.