Yes, the optional module would be a good approach, because one objection to having a fully populated system map by default that I have heard and that to me makes sense is that some players like to uncover a system one body at a time, and check on their progress by looking at the system map from time to time, so not fitting that optional module would solve that issue.
With regards to the idea that the old system map reveal gave too much away, I don't really buy that, as the FSS gives away all that information, just in a different format. Markers on a line that can be identified with practice just as easily, and perhaps with even greater accuracy than the graphics that were presented in the system map.
I do think that it's reasonable to have players who want to harness the power of the FSS (to locate potential POI's) to have to actually use it, in other words search for and locate bodies they are interested in using the FSS mechanics, not have targeting information taken from a system map reveal carried over to the FSS, but honestly, it's really not that difficult.
The overriding principle for me is that players should have a choice of tools to use to achieve things in the game, just as we do have in so many other areas. Different ships, different weapons, all can be used at the player's discretion in areas that are much more competitive than exploration. I really am at a bit of a loss as to why some players seem to care so deeply about how another person plays the game...