The Roman Numeral Kata

I've been pulling together a kata based on converting Roman numerals.  The idea is that after having people refactor this one to something relatively clean, they can test drive a different design.

I haven't settled on a good design just yet, though.  The concepts I want to drive home are:

• Excellent naming
• Small Modules
• Low Complexity
• Single Responsibility

Does anyone have a favorite problem space, or a solution to the Roman numeral conversion problem that really drives these home?