I'm developing an air app and I'm going to use a thawte certificate to sign it, but I would like to allow the user to add extensions/plugins at runtime (SWFs with a combination of vector and bitmap and graphics), so each user can customize his app.
What would be the safest way to achieve this ?
I was thinking maybe download the extension to the storage folder and load to the app, but would this be a safe approach ? Would there be a way to use my thawte certificate with my extensions ?

I appreciate any help you can give me in advance.