[iKnowKungFoo]

"there needs to be a temporary (6-12 months) solution that manages the existing content."

Famous last words. I once found an egregious security violation at a previous employer. Was told it was a "temporary fix" that's been going on 7 years.

You might look into putting all of the static files into source control, but ignore the folders full of uploaded documents (the videos, etc.). Then you can at least track changes and deploy updated HTML via a managed process. You should back up the large files and figure out how you're going to serve those.