A bundle event is already part of the packaging. It references files by their MMR root hash. By using mmr, relays can be sure the publisher isn't lying about the number of chunks and that a chunk is exactly at x position. The chunk size is fixed. So relays can choose to block a chunk if its part of a huge file. Imho blossom isn't needed. Although relays specialized on storing big events could rise, the napp files tend to be so small that we write them to the publisher's outbox relays.