Daniel, that seems more complicated that it needs to be.
We just need to create a CO that resets soft-takeover for the given control, then the XML needs only map that message to that CO like any other Mixxx control (and it would work in the GUI mapper.) e.g. <control> <group>[Channel1]</group> <key>st_ignore_next</key> <status>0x90</status> <midino>0x7F</midino> </control>
Daniel, that seems more complicated that it needs to be.
<control>
<group> [Channel1] </group>
<key> st_ignore_ next</key>
<status> 0x90</status>
<midino> 0x7F</midino>
</ control>
We just need to create a CO that resets soft-takeover for the given control, then the XML needs only map that message to that CO like any other Mixxx control (and it would work in the GUI mapper.) e.g.