Another problem with the case labels is that it is hard to find a shortcut for checkered patterns, which can be expected to be a common case. For Elk Chess it would be annoying if you have to write 32 case labels of the dark squares for the N move, and the other 32 case labels for the R move.
Using wild cards, it could look like this:
[aceg][1357]: [bdfh][2468]: R; *: N;