This answer comes late, and will maybe not 100% answer the initial request. However, the basic feature can be obtain by using a specific applet (using it now with 3.0, used it in previous versions of Cinnamon as well): Workspace grid (2D) and switcher.
When active and added to a panel, this applet actually lets you define a “real” workspace grid (number of rows / number of columns), and provides an option to “Use Keyboard shortcuts (Ctrl+Alt+Up/Down)” to switch desktop rows”. With this option checked, it actually overrides shortcuts for “Toggle Expo” and “Toggle Scale” to switch between workspaces (and you will be able to move windows to workspace up/down with
Note however that it seems to be possible to still keep the option to have shortcuts for Expo/Scale, looking at the comments on the applets page.
Ok, so simply replacing 'switch-to-workspace-up' and 'switch-to-workspace-down' by 'switch-to-workspace-11' and 'switch-to-workspace-12' in the "applet.js"-file , assigning shortcuts to them via "keyboard shortcuts" in "system settings" and checking the "Use Keyboard shortcuts (Ctrl+Alt+Up/Down) to switch desktop rows" option in the applet settings got everything to work. Now I can specify shortcuts for expo/scale and move up/down separately. Nice!