Apart from the size of the document, there is no limit on the size of the array or the depth of nested data. We plan on substantially increasing the document size limit.
I suppose this is due to the FDB limitations, so this obviously isn't a blobstore nor will it ever be (?). For example, we need to store video and image files which are easily 100KB - 1GB in size. Tigris or FDB are great to store metadata in (and the metadata is just as important to us as anything) but the blob storage is a bit of a problem. Would be interesting to integrate something with, for example, MinIO or S3.