Original Open Street Map lacked buildings and possibly Google Maps could be out of date, buildings missing, so I went to Koordinates at LINZ and got the property plan layer showing buildings for this site and downloaded it in DWG format.
I then created a layer using MapTiler with all the current buildings on the site. If I had the services information I could have added this information onto it too.
I then created a layer with Maptiler and overlaid it onto the map. From exercises so far, Google Maps only allows 30x zoom with Map Tiler, which is still a little indistinct but if you click on BLUE 32 icon and click on Level 1 Plan this takes you to an overlay of the floor plan of that building on google maps.
On both the overlays, in the top Right hand corner of the map you will see a FADER BAR that will fade out the overlay and show the map beneath.
The pop-up box has links to other data sources, and can display simple data about the buildings as well as photos, this is useful to someone visiting the site for the first time and who needs to check that they have the right building that they are to work on. The links will take them to other relevant information.
The link information is held in a table in a database. This can be downloaded to CSV, altered and uploaded again, so no major programming skills required to keep the information up to date.
Actual documents, PDF plans, PDF docs, scanned maintenance manuals, photos can be stored on the server, so large file directories do not need to be uploaded to database table (if they are they could slow down search/load functions)
On this site, as it is controlled at the perimeter, there are no street views of the roads and buildings within the site. You could use panorama photos (see these blogs
Overall, I think this is a useful tool. With a template it is easy to set up. You can get the Long/Lat coordinates by using Google Earth/Google Maps (clicking on point, you can get coordinates) so actually setting up all the building locations is not hard.
As the Database tables can be imported/Exported as CSV files they can be easily updated in Excel by general staff with no programming knowledge and a simple batch routine with some SQL could do the updating process in the database (or a simple You Tube video).
Having a security login interface to the website with the maps is not hard and this can allow for different user access to the data ( View, download or Admin rights etc).