I agree with some points. Like the overheating and the hardware side (getting it compact robust finding a good powerbank/battery) in general as I pointed out before.
In general the goal would be getting a somewhat working version which people could build on there own, not a polished consumer solution.
A somewhat cheap and dirty alternative for people to build it themselves, too get raw dv files without tapes. The main pitfall is, IF the firewire pcie cards work on the pi. If it works, THEN the software side for a diy type of setup is not too hard. I am not talking about a perfectly polished solution with the perfect UX. As I said if the card is detected and the necessary kernel modules are there and loaded, then dvgrab(
https://sourceforge.net/p/kino/code/HEAD/tree/trunk/dvgrab/) should be working, which can be installed via packet manager in almost every distro. Therefore the complex part, like implementing the driver and codecs is already there. I captured all my tapes via dvscan, because the windows 10 driver for firewire simply does not work. Maybe one could even get the functionality as a library, they seem to use it for "kino"(which it is actually a part of) from glancing over it.
A simple python web servers is no magic and is setup pretty quickly. Running dvgrab via subprocess isn't as well (with fixed parameters and fixed pathes and timestamped filenames to start with). Again it is dirty but should be working. Video streams of previous records should be possible on the limited hardware as well, considering the low resolution of the cameras targeted. Safety is not a concern either. It has it's own local network and is not reachable from the outside.
All of this is purely hypothetical without knowing if these cards work properly on that type of arm computers, that is what I meant with "thinking too much ahead". If it does not the journey is over.
After all this would be just something "neat" to do and more or less just something to tinker.
Edit:
The "goal" in some unknown future would be some kind of resource like:
Buy this board, one of these powerbanks and one of these pci-e firewire cards. Here is the model for the case, print it or let somebody print it for you. Install this software. And feel free to modify it to your needs. So some sort of diy guide.
Edit 2:
Again take it with a grain of salt: Everything is easily in theory for devs until they actually have to do it.