Well now that was a radical move doog - I don't think I'd do this. I'd probably paint over - I heard American vehicles can have A LOT of paint layers on them, as they are frequently repainted. Once I had a similar problem - if I pose two M48's side by side, one of them is Army and the other is Marine, could I tell them apart only looking at the color? And what would it look like? I asked Doug Kibbey and he forwarded my question to his friends, and the answer was Marine green was greener and lighter than Army OD, and it tended to fade to an almost pea-green shade. I was told this was often accelerated by the soldiers washing their equipment with fuel mixed with green paint - this "renovated" the paint at first, but then it faded...
I say the choice of preshading color will be critical here. Army OD should be almost not green at all from what I heard, whereas Marines color should definitely be green. So probably dark grey, maybe with a little blue additive would do the trick? For the centers of panels I'd go with a light shade of green. I'm not quite sure about the "scale effect" but could be it kicks in here. Plus we expect the paint to be faded right?
Another option to consider, if you're going for that "red dust" effect would be to preshade in red/brown right away. The red dust would deposit in the crevices first, so it works - the recessed parts ot the machine are covered with red dust, the centers of the panels are somewhat cleaner/greener, dusted off by crew walking, plants rubbing and the eventual wind. On the other hand there are many fotos of Marines moving along sandy beaches - in such case the weathering should be rather sandy sand than red.
Hope it helps and good luck with your project
Paweł