An app like that could be built, but it would require more than just blossom. servers only store and serve blobs which are chunks of binary data. there are no file names, tags, folders, or anything else you would need for a personal cloud app
Also blossom isn't private, its the opposite of private. its designed for the blobs to spread around multiple servers, backed up, and still be available event when the original upload is taken down. so probably not something you would want for a personal cloud
All that said, I think there is an opportunity to build a "blossom backup" tool that would let you see all the media you have uploaded and back it up on your own computer