Hello @TheAlbionist I kind of built a specific multi-select component for UD which there is much discussion on here:- New Multi or Single Select Component for UniversalDashboard just throwing this out there as an alternative without any code to work on…I hope this component makes it to your dashboard as seemed to have helped quite a few people so far obtain multi selected values 
more info and function UDInput select drop down with multi-select?
This is another alternative:- Out-UDGridData with selectable rows?
If neither of these suggestions float your boat, then please share the code you got so far…Thanks and keep us posted