What you are trying to achieve is very simple. You can just make Buttons that inherit from SecureActionButtonTemplate and assign it an action slot that is the same as the action slot on your actual action bar button. It's 1 for the first button on first bar 2 for the second, 13 for the first on second bar and so on. Using SacureActionButton should basicly make it behave like actionbar button and using exiting action slot should show you the exact same spell that is on the other button with the same action slot.
Code:
button = CreateFrame("CHECKBUTTON", name, parent, "SecureActionButtonTemplate, ActionBarButtonTemplate")
button:SetAttribute("type", "action")
button:SetAttribute("action", slot)