Yet another possible use for IndyFont! http://forums.adobe.com/message/4623594
All it needs is a custom slashed zero, stored under the regular code for a zero, and a GREP Style to apply your custom font to the zeros in question.
An additional advantage is that the ACTUAL character still is a *zero*, not the capital slashed letter O.
You can get the demo right here on the forum at Adobe Community: [Ann] IndyFont Demo: make your own (1 character) font
But we ARE still waiting for the full version.