Might be tricky because airbags are single-use. How do you know that your hack worked? If you test it to confirm you lost the air bag, so you'd have to buy at least two, make sure you did the exact same modification on the second one after confirming it worked on the first, and still be unsure if it's actually going to go off when it matters.
airbags are single-use. [...] If you test it to confirm you lost the air bag
Please try to avoid presenting your hypothesis as fact. If your third sentence was phrased as a question it'd be fine. Currently it's misinformation.
Of course it can be tested without destroying it. The actual air bag component could be disconnected from the rest of the device and the connection point monitored for the appropriate voltage/current required for activation.
And then you can never be sure you connected it back properly or if there was some anti tamper mechanism it tripped. Probably not, but wouldn't risk my life with it.
Or just buy one of the other vests that use a simple tether and doesn't require a stupid fucking subscription and a additional, complex point of failure?