Actually, I spoke too soon. Looks like there is already a JS event in ACF Pro for handline this situation. The event is:
render_block_preview
It passes two arguments, the element as a jQuery object and details about the block (name, content, mode, etc…). I put together a quick example usage here:
https://gist.github.com/hereswhatidid/a67dc3697a481c223bdced42586f6664
