Best of luck with this; defining the problem in this case seems almost as hard as devising a solution, perhaps even harder.

There's an excellent introduction to chess problems on the British Chess Problem Society website, it suggests that a good problem consists of six basic elements:

1. a position
2. a stipulation
3. one or more intended solutions
4. difficulty
5. a theme
6. originality

Anyway, I'm interested in what bugs you think might exist in Chess.pm - can you give an example?