While it's now in the mainline branch, Peter Hutterer, the chief developer of MPX, hasn't stopped there. One of his most recent accomplishments was modifying Compiz to support Multi-Point X. In his personal git repository, he now has a custom version that does support multiple inputs and multiple events occurring simultaneously while still enjoying the wobbly windows and other desktop effects presented by this window manager. To do this, Peter had to rewrite portions of the Compiz Core to support XI2 (X Input 2) by replacing some functions and listening to X Input events instead of internal Compiz core events. Additional work was then also required to support the Compiz plug-ins on MPX.
In a blog post by Peter explaining this Compiz+MPX work, he mentions that many details are left in an unfinished state. Unfortunately, due to time commitments, he won't be continuing this work with an MPX-aware XI2-supportive version of Compiz. Perhaps someone will step up to the plate and finish it off and down the road be able to merge it into the mainline Compiz.