I don't think that supporting MIDI files is feasible as the developers would have to add a wavetable synthesizer or lots of instrument samples to MM for Android. MIDI files aren't sound files, but only contain instructions for a sound-producing device.

Think this is needed as ie does not work on android and i can not find any browsers that will play web page embedded midi files or other Ms plug in needed files.
So maybe you can get mma to see them and either play them online or download them for playing on the phone or tablet. :)