Hey, This is not possible, unfortunately. Bungie does not support the transfer of save data between accounts. As you noted, the only option is cross-save which allows you to access data from one account on a different one as long as the feature is enabled. As Swat pointed out, however, it is not possible to cross-save between two accounts on the same platform.
You cannot move to another account on the same platform. You can only move to another platform. Example: Steam - Steam? NO ❌ Steam - Xbox? YES ✅