I tried it and found that I had to update SPJS-Casc.js to support setting a mulitchoice people picker in the setFields. Download the attached file, rename it to SPJS-casc.js and replace the one you have in /SPJS/DFFS/plugins.
Now add it like this in your cascading dropdown config:
"setFields": [{
"from": "YourMultichoiePeoplePicker/Name",
"to": "YourMultichoiePeoplePicker",
"parseFunction": "parseMultiPP"
}]
and add this to your custom js:
function parseMultiPP(a){
var arr = [];
if(a.results !== undefined){
jQuery.each(a.results, function(i,user){
arr.push(user.Name);
});
return arr;
}
}
Let me know how this works out.
Alexander