Revit does not currently have a Key Plan Tool so this is what we do when we need a Key Plan on our sheets.
1. Export your Base Plan to DWG (just the unit boundaries)
2. Create a Detail Component. File... New... Family... Detail Component.rft
3. Import your Base Plan. File... Import... DWG
4. Add a Yes/No Parameter for each unit or quadrant. Family Types... Add Parameters... Type Yes/No... Set Instance Parameter... give each unit or quadrant a name.
5. Draw Filled regions for each unit or quadrant of your Base Plan and assign each one a Yes/No Parameter. To do this go to the Filled Region's properties and you'll find a Visibility check box. At the far right there is a tiny grey box. Click on it and select your new Yes/No Parameter as the parameter that defines the visiblity. Do this for each filled region.
6. Now load your new Detail Component into a Legend View in your project and set the appropriate scale.
You can now turn on and off each quadrant using the Yes/No Parameters you set up in the element's properties.