If Republicans aren't able to get a two-thirds majority for their 12-4 redistricting scheme in Ohio, the measure can be annuled by a referendum, after which a court will then draw the new map.
The following is an attempt to construct a viable map that a court might favour, having some regard to the existing districts but more regard to compactness, county lines and community links.
I'm writing this in north east Scotland and have never been further west in my life than Snæfellsness, so I can't with confidence define where the important community divisions lie. I've therefore decided to use quantifiable data as my starting point, namely Combined Statistical Areas (CSAs) and Metropolitan Statistical Areas (MSAs). See here for my dataset
Using these as my basic building blocks, I've come up with a map that creates six safe Democratic seats, five safe Republican seats and another five seats that could plausibly be won by either party.