Yes, we should be using EXR for the intermediates + some sidecar json file for passing the metadata. Presumably this should not be a difficult enhancement of the feature so it supports sequence rendering. Prores4444 was working for us for some time, but I have noticed recently that there is definitely great overhaul now with generating review files.
I really like this workaround and it reminds me somehow a feature we were discussing here a while go. So instead of Client review it would be something like Remote publishing. I will explain it more in depth. At the moment we are setting the Nuke render instance publishing either as Existing, Local, Farm target and the process of publishing with review file generation is either Local or Remote. So if we are publishing Existing and Local it is rendered and published at the local machine and if it is set to Farm all is submitted to Remote.
We could perhaps split those processes and move the overhaul of generating reviewable files and integration into the pipeline to always be processed on Remote. This would be covering the topic here too Nuke - Publish on Farm with Existing Frames