Changing signature algorithm of keystore, possible?

Basically I have a keystore file, which has been generated with -sigalg SHA256withRSA.

This, I've learned too late, is bad for older Android devices (although Google Play gives zero errors when uploading).

So I was wondering if it is possible, in some way, to change/regenerate the same keystore, with SHA1withRSA instead, keeping the same SHA1 fingerprints in the process.

If that's not possible, perhaps it's possible to create a new one, based on the old one, and achieve the same signature.