MOI on the other hand is already tied to MEX at the full grammar level. So I am not sure what it means to say that you cannot use MEX with MOI. Almost anything can be used with MOI if you first turn it into a sumti, and then apply a ME conversion to that sumti. You can of course turn a MEX into a sumti using LI, so "meli MEX" with appropriate terminators should work with MOI. I just tried it, and you need either a lo'o or a me'u to terminate the li/me construct before the moi.