You might try [detonate]. It will open multitrack files. It all depends what you need to do with it, but [detonate] isn't a sequencer. It also doesn't seem to recognize controllers, but I may not have seen how to do that.
what i need to do is _explode tracks and _detonate them into different kind of messages such as notes, velocity, and channel, so [detonate] is built exactly for that. i forgot about detonate because that is the first time i am doing something with midifiles in max.