Yes it is possible a large amount of data, the types of data wiuthin the data aseets and, if there is interconencted data assets referencing one another. Which may leave behind a redirector.
Is there already a redirector there, Have you tired running fix up redirectors across the project first, before attempting the conversion?
Are there any other errors in the Log file just before it hits the critical failure?
My initial thoughts would be to create UObject versions of each of the data assets, keeping the same inheritance structure as the UDataAssets.
Then create an editor utility which can loop through all your data assets and see if they are a type of UDerivedDataAsset1 map it to the new uobject type, and call a c++ blueprint function librayr which will follow pretty much the save code as ExecuteChangeDataAssetClass, with changes to how its spawning the blueprint version of the new class.
I’ll do some more investigating into what that code will look like and get back to you.
Regards,
Keegan Gibson