I checked some of your older posts an saw that your panel has barn doors. Small windows. That will give a very limited view if you mounted the rear seat backward. If you had a tailgate style then rear facing would give good views making rear facing a better option, but with barn doors the windows are small and also a bit high up when in the seated position. Granted even a small view is better than none but still the passengers would not be able to see much. I personally get very motion sick riding backwards but it makes it that much worse if I cant see anything. But then again I get motion sick regardless if I'm not the driver.
If you mount them as 3 rows you have the drawback of how to get there as you posted. If you mount them against the sides facing center, then at least your passengers are facing each other making conversations easier and speaking face to face gives you something to look at other than only the back of someones head in the dark.
So I guess my opinion would be if you are going to mount all 3, I'd go with mounting sideways. But that all depends on how often that many ride with you.
Another thought.... What if you mounted the seats using recessed mounts. That way you could mount one seat as a 2nd row seat for normal driving. Leaving the rear for cargo. Then when NEEDED have mounts ready to run both as center facing. Your own version of stow and go seating. Maybe.