The IMDb "My Movies" enhancer script is so useful that I just restored Firefox back to a backup from last week to restore the highlights.

My vote would be for a quick-and-dirty temporary solution, such as user downloading the .CSV files and then uploading them back to the script, even if this is by no means a long term solution. Because, anything is better than nothing.

I would definitely be willing to contribute.

Note: I only main a handful of lists, of which "seen movies" is the largest and most frequently modified. I only update the highlights a couple of times a year.