I've just looked into AMS features and format.
It seems and extended XM with its shadowed instruments, vibrato (pitch) envelopes, etc.
Altough it has some very unusual features (varying track number for patterns, max 7(! my god..) effects per note, etc.) that seem totally needless for tracking, it does not seem impossible to be supported.
The only worrisome thing is the echo effect. As far as I remember it was mentioned in the tracker user guide but not in the format descripton.
I never said it would be perfect - but at the same time, I strongly doubt that MilkyTracker would do any better job at it. And unless the author of MPPWC wants to rewrite his engine completely, he will also not managed to do a better job than OpenMPT, as the "best" format supported by both players is IT.
While converting an imported format to an own, (and hopefully superior) format is unavoidable in a tracker, it's not necessary in a player at all.
The base problem is that even if a superior format contains all features of another format, it does not mean they are fully compatible. Different trackers may handle (not only) side cases differently. For example, MultiTracker is claimed to be Protracker-compatible, but it's easy to create a sample case where Pro and MultiTracker plays that differently. The same goes to Scream and Impulse Tracker, e.g. defining global volume in IT affects all currently playing channels while only newly started notes in ST3. Even handling the default effect parameter is different between them, etc. There are hundreds of such small fries... (so creating a super container format is impossible.)
In MPPWC, one of the goals was to play each format as if it was played in the corresponding tracker. So it does not convert any supported format to a common internal one. It's core player engine deals only with things that are very basic for each format: BPM, speed, tracks, samples, presence of effects, mixer, and so on. Rest of the playing logic (along with the loader code) is implemented separately for each format. The latter requires reverse engineering trackers. This is what should be done to Velvet Studio as well but it is the most time consuming part.
It depends on how much rev engineering needed, etc.
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