I have had some success using:

-vf fieldmatch,yadif,decimate

with ffmpeg. Maybe there could be an advanced dialog to specify complex options/parameters to ffmpeg and specific filters? Or maybe not? It could easily become to complex and would probably be easier to just preprocess the file with ffmpeg outside of DoM.

Probably related to 0000573

For users familiar with FFMPEG, it could be nice to be able to add any FFMPEG filter chain with any options desired - much like Handbrake allows manually editing encoding parameters as raw command line-style text.

One can pre-process files before bringing them into DOM, but it's faster to do everything in one pass, especially with large files (e.g. 4K ProRes4444HQ) and if the drives aren't SSD, so there's a large overhead to reading/writing files. So if this was easy to add, it'd be a bonus.

To most users the FFMPEG options would be absolute jibberish, so maybe it wouldn't be advisable to make this setting too easy to find!

PS I've also found fieldmatch + decimate can work well, but it often needs the fieldmatch options tweaking to get a good result.