following up your suggestion, I actually implemented the feature lately. If you download the last version of the plugin, you will see an "EmbeddedFloorMaps" folder where you can put your json files:
and also a EmbeddedThumbnails where you can place the thumbnails for them.
Then launching the scene the user will have a wizard and will be able to select your floor maps:
I hope this is gonna suit your needs.
thanks!