What you describe can not be done using bind mounts or links. However, you can use
overlayfs mount will show "a merged filesystem" containing files and directories from both. The upper filesystem takes precedence over the lower filesystem. If file exists in both, the upper filesystem version will be visible, in case of directories they are merged. Writes are made to upper filesystem (files are copied from lower to upper if they do not exist in the upper filesystem).
In your situation, use
/home/mvanorder as lower filesystem and
/mnt/data/home/mvanorder as upper filesystem.
Note the behavior on deletion: changes are always made in the upper filesystem instead of the filesystem(s) where the file exists. A whiteout file is made in upper filesystem when a file is deleted on overlayfs mount. A whiteout file makes the file invisible in the overlayfs mount. When a new directory is created in overlayfs, it is marked opaque. On opaque directories, only the upper filesystem version is used, even if a directory exists in lower filesystem. This means when you delete a directory in overlayfs and then re-create it, only the upper version is visible.
Exact details about
overlayfs are explained in the documentation.