There are two different methods that JJP has used to add buffers to the 7.5V design.
There are tiny boards that have only the buffer IC and a couple of connectors on them to piggyback on the unbuffered boards. They will also have a small wire, usually blue, running from the buffer board, across the main light board.
There are also 7.5V boards that have the buffer already on them. These are harder to see just by glancing at them, but you could tell by the board rev. In the manual, there are schematics that you could use to determine which revs include the buffer. You will not see the same rev throughout the game since the small, single LED boards have had more revisions that the bigger ones.
I have unbuffered 7.5V boards in my game, and I have had two cases where the lamps locked up, requiring a reboot. I reseated the cable where I suspected the problem to be happening, and I have not seen the issue in over a year now.
One other issue that I have seen is an LED where the red segment died. This was on a game with buffered 7.5V boards. Even on the 2.0 boards (or any game with LEDs), this can happen.
I guess what I'm trying to say is that I think you're being a bit overly cautious.
Edit: Here's a picture I found that shows the add-on buffer daughterboard. You can find them on the multi-LED boards sometimes, as well.