There is no way to dead reckon with MEMS alone. Thermal noise alone make it's physically impossible, no matter how many sensors you use. Simply put, even under the most ideal of circumstances in the real world you will over time gradually drift from being certain of your location into a greater and greater degree of uncertainty, and it's not correctable without using other types of sensing methods such as optical, magnetic or RF. The drift error is due to both the thermal and gross mechanical noise present, and it can't be filtered out in a real world device, unless perhaps you're able to map the entire subatomic structure of the device you're using and incorporate that into the stabilization algorithm =>. Multiple sensors in various alignments is going to require a very high precision mechanical setup, which ends up just compounding the mechanical noise problem, though it can increase short term precision significantly. You really have to have some other method of true dead reckoning. MEM's is only good for transient movement in between, or short/medium term lapses in the true dead reckoning measurement.
The human sense of balance is a good case study. While most people think of the inner ear when they think balance if we don't have optical feedback on our environment we lose our bearings quickly, as anyone who's ever played pin the tail on the donkey, or pinata can attest to. When you put the two together it's really amazing.