Unfortunately, things are not that easy: actually my mopho isn't rooted. And yes, before you ask how I'm moving it to /system, what I did is to un-sparse the system.img from stock. So, now I mount, modify, re-sparse and heimdall flash using a script of mine. Problem is as everything is still stock I've almost no way to debug or troubleshoot anything live.
Back to the point, I think this is a strange way of doing things. I mean, I thought the "rule of thumb" for .so was to always default to /system/lib unless an update for the given apk was installed (in which case, /data does come into play).
But doing things like MXP does seems strange and at the same time makes me think one could never integrate MX into any ROM. This because MXP *always* searches into /data (as per your comment) and only way to move/copy/symlink into there after a data wipe/factory reset is a bit tricky. Any other way you could think of? I'm open to alternatives.
Finally, I could see lots of guys out there wishing to put MXP as their custom ROM player. Are you MXP devs planning to somehow make this easier? Please don't get me wrong, I'm asking kindly and in no way telling you what you have to do or "claiming" unpolitely.