It wouldn't be too hard to build the OS for the Amlogic sources, although CE is probably a better starting point since they already use the same Linux 4.9 kernel sources; the challenge is the lack of git history in what's been shared so good luck in finding which of 350,000 files has been fiddled with by the TV vendor. Mediatek is a total unknown. However the issue won't be kernel, it will be the boot environment. I'd be surprised if the bootloader was not encrypted. This normally rules out most tinkering. Also, we're happy to break Raspberry Pis and such, but I'm not sure anyone on staff wants the responsibility for bricking a users TV so it's not hardware we'd investigate.