The Voyager 2 will use custom PCBs for the HAT, but it will still be on top of the Pi.
In the next iteration, I'd like to use the Pi Compute Module to migrate to my own custom board, but I'll need to work with an EE firm on that, since I'm not knowledgeable enough about EE for that kind of project.
All existing CSI bridges that you have used so far have two very serious problems: they do not work with audio capture and due to HDMI backpowering, your Raspberry may stop booting until you physically disconnect the cable. Backpowering is especially common when using KVM switches and some HDMI converters.
Both of these problems are solved on v3 HAT, thanks to our CSI bridge design. Are you planning to solve these problems? Just interesting :)
There's no audio support, and audio would be a nice-to-have, but it's not my top priority at the moment.
I'd like to integrate the TC358743 onto the HAT itself, but Toshiba's got a huge lead time on orders right now.