If you really want to edit the M2T file, you can get the MainConcept plugin.
However, the change from M2T to Cineform is practically lossless. And the conversion back is very clean.
I suggest you try it out and decide for yourself. It also depends on how you plan to distribute it. If it will be played back directly from the camrea, it might be noticeable if you look really hard. If you are going to do anything else, it probably will not be noticed.
Steven
Adobe Premiere Pro 1.5.1 / After Effects 6.5 Pro https://www.stevengotz.com
Learning Adobe Premiere Pro 1.5 https://www.lynda.com
Contributing Writer, PeachPit Press, Visual QuickPro Guide, Premiere Pro 1.5