Well, I am open to suggestions, but I could not really think of something that would still be palatable. For normal leapers and sliders it is easy enough, because intuition is shaped by experience with orthodox Chess, and you expect stretches of consecutive destination squares to be slides that can be blocked anywhere between the source and the destination. So showing those on an empty board is fine, and showing virtual captures in another color even though the board is empty solves the problem of divergent pieces. Chess players still tend to think of empty squares diagonally in front of Pawns as being attacked by that Pawn.

The problem is with lame leapers (the marker indicates the moves don't jump and can be blocked, but where?) and hoppers (locust capture really being a special case of hopping). There occupying a square does not only have effect on that square (as it would have for a potential capture to that square), but can enable a etire series of moves (e.g. capture to all squares on the ray behind it for the XQ Cannon). And in principle you can have hoppers that turn corners (see for instance the 'sandbox' diagram I posted with the article on Betza Notation), so that occupying a different square on the primary leg would enable an entirely different series of actual destinations. In general occupying a square can enable multiple destinations, and a destination can be enabled by occupying multiple squares. It is really a mess. In an interactive diagram the reader can always set up a position he wonders about, though, and see what moves the diagram allows there.