Thanks for the detailed overview of your scenario. It gives us a good idea of a real-world usage scenario.
From the standpoint of the Map widget we need to complete our support for static image overlays.
The size of the images might or might not be a problem. Even if they're large they can probably split into smaller areas.
Since you're starting with vector data it might be possible to convert the floor plans to a GIS format such as Esri Shapefiles.
From there, we can complete the conversion to the more web-friendly GeoJSON format.
This has the advantage of reduced size as it deals away with the large images.
It also makes customizations harder, as you can't simply paint over them.
Individual features and areas should also be available as GeoJSON outlines.
Please, let us know if using GeoJSON for both the schematic and features makes sense.
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