what did the addin do?
If it was largely based on existing tools in arctoolbox replicating in python would be easy
If it not on the path that python covers, you might look at other options
Thanks @DanPatterson that reference is very useful. In the main much of the functionality is normal tools i.e. split polygon but then it does a whole lot of attribute calculations based on the actions. I think with a bit of trial and error using the tools and the SDK will get the results needed. Cheers Dean