This may work (have not tested this out):
1. Recreate schema in template part
2. Add any data connections/resource files that you wanted in there
3. Copy all of the data from the .xsl file into the new .xsl file
4. Copy mafiest data over.
5. Going to test this out right now because I'm interested and I'm sure I am missing something that will pop up
Edit: Something popped up. Infomartion gets added to the .ict file of a Template Part (buttons and probably other unbound controls), so this would be not very fun to do.