1) we do not reccomend you try this
2) it will void your warranty and we would not be too excited about doing any out-of-warranty repair
Now for the practical . . .
I do not remember for sure, but as I recall the film has to be rotated 90 degrees, not 180 degrees. This means that you would have to find a larger sheet, or there would be some "seams".
The rear polarizer in the TFB is transflective, that means it is designed to TRANSmit light from the backlight, plus be reFLECTIVE for light coming from the front. The reflective property will block some portion of the light from the backlight.
The rear polarizer on the TMC is reflective, to let as much light as possible through. This is so because the negative mode does not let much light in from the front anyway, so the usefulness of the backlight is maximized by using a rear transmissive polarizer.
The end result is that the backlight will be a little dimmer.
Another thing to be aware of is that the front polarizer on the TFB is a "FSTN". The front polarizer on the TMC is "STN" so you may not get the same color as a TMC if you re-use the polarizer.
You do not want to make it anything other than "optimal". Typically we pull the front polarizer off the glass, reassemble the module, then experiment with candidate polarizers and angles. Once there is a good one, mark the angles, trim it and reassemble it.