It would be hard to find manufacturers to use it. None of the existing Android phone manufacturers would be able to release phones with this fork without also abandoning the official Android platform on all markets. Google are very strict with this in their tos. You cannot release devices using non official Android builds without losing your right to use GMS and Android Brandice on your other Android devices.
They mention that there are mitigations in the kernel nowadays, so the mitigations they turned off here are now redundant. But I'm uncertain if that refers to the same cve that you mention.
in Sweden we use them a lot. Most of the time they work really well and it's not like they are useless just because it gets really cold. They still help a lot even if the traditional heater element might need to kick in for short periods. It's usually not until 20 below freezing that they don't add much, but those temperatures are not a daily occurrence for most of us.
You can do this in any shell already by placing the other language in a separate executable file.
With everything in the same file the risk of ignoring the separation of concern principle (each unit should do one thing and do it well).