I would not mess with the internal mics. While the mics don't sound that great for music, they have very low self noise, around 18dBA. I believe these are Primo mics (Singapore). Primo is known for some of the lowest noise electrets around.
I have been tempted to take the mics out and use them for HRTF recording (over the ears, or just at the sides of the head, in both cases pointed forward). Never done this, but it would be great for recording ambient sounds, streetscapes, lectures, etc. Other people have used a baffle to get more separation from the built in mics.
As much as I love modifying gear, I would leave the M10 alone...
Richard