Dash/hyphen in preset name breaks theme function naming convention

For example:

If I have a preset named thumb-small imagecache wants me to use this function name:

imagecache_formatter_thumb-small_default

But dashes aren't allowed in function names.

These are my suggested solutions:

Either dashes(or any other character that isn't allowed in a php function name) shouldn't be allowed in preset name or those characters should be cleaned out when defining theme functions.