Why C++ instead of a higher level language like Python? The developers could focus more on game functionality than C++ bugs and cross platform issues. Performance should not be a big concern for running an old game on modern hardware.
Rule of thumb suggests that implementing AoE with Python today probably means PyAge2 runs about as well on a 4.5 GHz CPU as AoE2 did on a 266 MHz Pentium II. (not that well)