upgrading to BI 4 .unv to .unx migration

I am just starting a project to upgrade from XI 3.1 (SP6) to BI 4.1 (SP3 probably).

Switching to UNX universes is something we would like to do. We can create them easily enough in the Information Design Tool (IDT). I say easy but there are a few hundred but it's manageable. The concern I have is how to convert thousands of Webi reports (we mainly only use Webi) to use the newly created UNX universes.

Currently I think I have 3 options:

1. To open every report and manually change each query in the report to use the new unx universe.
2. Get someone to write some code to do point 1 using the SDK. I know I may not get all of the variables correctly matched but it could get 95% of the reports correct in a timely manner.
3. Find a utility that someone has already written or is commercially available that would do this.

Can anyone help or advise on this please?

Thanks in advance

Nick