SQL 2005: Creating Correct And Incorrect Versions Of A Database

I work at a place which is currently running SQL 2000, but they are
planning to migrate to 2k5. I was thinking that this is the perfect
opportunity to fix all the weaknesses we have had in our data model for
the longest: primary keys and foreign keys with different names, use of
character columns for boolean fields, use of integer columns for
toggles, no referential integrity, etc.

So, even if I create my Utopian perfect data model and modify all of
our data loaders to use it, our live website must use the old incorrect
version because there is way too much work involved in redoing the
code.

My question then becomes: if I have a correct version, how easy and
with what approach would one take the data in the correct one and
mirror it to the poorly designed schema?