Here's an answer 2.5 years too late:
I don't know anyone who will remove the extra "multiformat" framelines, but I will tell you that I use both the Mamiya 6 and 6MF.
The other day I shot the whole day with the MF, but when I got home and wa taking some notes on exposures, subjects, etc., I honestly couldn't remember which body I used that day. I simply did not notice the "extra" and "distracting" MF lines at all in real shooting.
CONCLUSION: I only shoot 6x6 with the Mamiyas, and those square lines are the only ones I notice.