Let me explain why I'm against it.
If you use direct access to the servers to the same store, this is a long time (large files pulled from the current server and so not fast). This will lead to difficulties in the network.
If you have in mind their own store on each server, they can not be identical, because servers have different access to the documents, that is some of the documents (and their attachments) can not be replicated.
Your idea is contrary to the principles of Lotus Domino.

I like the idea but do not know if I should Promote or not. It is definitely a super interesting idea, but my guess it is difficult to implement it and I would be scared myself if the companys only daos-store got corrupted or anything like that. Imagine one server in the cluster go mad and delete attachements that is forever lost and then trying to restore this from old backups.

Well, using the logic of current development, the single DAOS option would need to be atomic. That means the back-end would then need to be a clustered DB2 store, which would cause clients to re-architect their entire Domino infrastructure. Do not see this happening. Though interesting, that would create a lot of excessive LAN traffic as well, causing further delays, over looking at local storage for the file (physical or virtual).

i see the logic of the idea, but this would only make Lotus Notes data run even more slowly.