You could create and input_boolean, then make a quick automation that when triggered turns light on/off.
Then you could use the input_boolean ID in the svg.
Or try grouping. Select both objects (select the first, then hold shift and select the second), and go to Object → Group to put them in a single group. Then you can give the group an ID. (although these will still have same css class)
Or try the new camera fork of floorplan which I believe allows 2 sort of instances (havnt tried just yet)
best of luck