A while ago while working on batches of video edits, I came to the realisation that frameserving is simply the best, most flexible way to encode in some cases. Time marches on, and so did my software - eventually I came to a new machine, new Premiere Pro and - disaster - no apparent support for frameserving. Just when I needed it...
Cleverer people than me have solved the CC2019 problem - for those of you editing in Premiere it's once again fairly easy to frameserve encode. However, it did take a bit of sleuthing to figure out a few things; this tutorial should help you to avoid the same problems I encountered.
November 2019: Vouk's excellent Voukoder plugin for After Effects and Premiere can now accomplish some of what this article covers, and it has an active developer and user community. Vouk includes the FFmpeg/libav filters to enable things like bwdif deinterlacing. There are still some bugs but it's worth a test - it should integrate nicely into an AME or batch workflow. More complicated workflows may still benefit from frameserving, so it's still worthwhile to do.
July 2020: wangqr, the developer of the dfscPremiere.prm patch, informed me by email that he's not maintaining it any more as it's been merged into the main Debugmode Frameserver repository. Download v3.0 for use with CC2019 and above. Thank you for your hard work, Q!