I think it would be a nice addition to be able to open up the battleground and arena scoreboard with a customizable click similar to the calendar.

I don't have anything against expanding the options for minimap clicks, but why the scoreboard? BasicMinimap has no option to hide the LFG button, so it's always shown. So why click the minimap instead of the button?

You're right that it's a bit of a funky request, but I personally hide the LFG button (using another addon) because I don't really like the aesthetics of it. Usually I just key bind the scoreboard function, but using a quick mouse button would be a nice change.