Yes you can stil, record in ProRes, and gain a less compressed video file. That said, I would just run a quick test, shoot the same scene, with a person in it, or a staged interview type shot, record it in camera on the best video setting, then record it on the VA. Take both files into your NLE of choice, and see which one looks best, and if there is any real gain in recording to the larger ProRes files. Then you can make an educated decision on the best way to go.
When I got the AF100 (also a 8-bit camera), we did green screen tests recording HD to the camera codec SD card (which is a lower bitrate than the OMED), and outputting live SD to our Video Switcher for a live key, recorded this, and then recorded a HD signal to a Hyperdeck Shuttle. Bottom line, the in camera HD 1080p30 recording aced out the live key for ease of keying and image IQ, and the Shuttle was a close match, with a much bigger file size, but once the project was rendered back to SD, there was no real difference.
So it all depends on how much you want to change the image in post, the ProRes file wil, be more robust here, and allow for greater changes. But if you are only making small changes, outputting for DVD or Web distribution, then you might not see any real difference or benefit.
Adding the Micro Converter (battery model has it own battery, the original mini will need 12 VDC from an external source, the Juice Link PreAmp, your rig is grown in size and complexity, and you have lost your hand holding 5-axis shooting ability, or at least dimished it.
I shoot interviews with the AF 100 or the Micro Cinema camera on a tripod, then use my PenF (similar camera inside as the OMED) handheld for B-roll to endit into the main shoot, with audio on the main camera. This way you get the "Best of both Worlds", which is what JB does on a shoot. The Oly OMED Mk2 is a great little camera, use it well, but understand its limitations, and you are "golden"
Cheers