If you read the link I posted above for Travis' awesome upgrade, he actually looked into that a bit, and decided it was not possible. The A2B bus is a proprietary bus from AMD and there are no publicly available tools. You have to be a customer of AMD to be able to get chips and information. If you can figure something out, that would be awesome, but it seems very hard.
If people only add a subwoofer like the Boost, I don't think it would be pointless, because simply tuning the sound by ear with only adding in subwoofer should be possible without really changing the characteristics of the stereo. Just to be clear- both the SR and premium LR stereos are highly tuned from Tesla. They really care about the audio quality and have done a good job of setting up their DSP for optimal sound. Travis did tests, and I did tests using REW and a calibrated microphone, and the stereos are nicely tuned Harmann curves with a flat EQ. BTW, the Boost box has a 10" subwoofer that can handle 500W, so wiring the dual voice coils in parallel can get you a lot more power out of the VADM1 if you need it.
One thing Travis did, and what I'm currently building out, is to route all the audio through my own DSP and tune it to match a new configuration. Especially in the SR, I only need to reroute front-dash, front-doors, back-doors to the DSP and I can then route the newly tuned signals back to the speakers. Lots of wiring, but in principle this is not hard. I'm using the TeslaOffer style speaker wiring cables to get convenient connectors to plug into the wiring harness without having to tap.
This will allow me to add in the tweeters in my car which are there, but currently disconnected. And also add in a subwoofer and more powerful amp for the front door woofers which can take 80W. I'm cautiously optimistic that I can really improve the sound. Hoping it will be worth this ton of work.