Adding Buttons & Layers to Slide Master

For me, additional slide masters rarely work. I usually have additional interface buttons like "video", "downloads", "simulation" and the like. These are enabled or disabled as required. Slide masters are difficult to use because:

• I need to assign a more complex or specific trigger than "next slide". E.g. Download a specific file, show a particular layer, launch a lightbox etc.
• There are too many possible variations of active vs. inactive buttons. Two examples:
  • Next active, Previous inactive, Video active, Simulation active, Download inactive.
  • Next active, Previous active, Video inactive, Simulation active, Download inactive.

Each combination would require a new slide master.

So I do it the "long way" and have the buttons on every slide.  I don't have a lot of trouble doing it this way because:

• I have a standard set of buttons and they never move.
• I set up my first set of buttons to the most common states and duplicate it throughout. The most common state is usually "previous" and "next" active and everything else inactive. This way I don't have make a lot of changes as I develop. It's usually just a case of enabling an additional button and assigning a trigger to it.

Not the most elegant solution but it's the only thing I can think of. If there was a way to change button states that are part of the master slide and assign triggers to them on a per slide basis I'd gladly do it that way.