The challenge mode sounds very cool. Obviously only need to buy the first one though, because the series went to hell after MMX4.
I wonder if it will include the Vile mode from Maverick Hunter X. For the uninitiated, the original game was already given an updated re-release on the PSP a few years ago with 3D graphics more similar to the later PS2 games. After beating it as X, you could play the whole game as Vile also.