@necrosis Ok, so the design requirements are:

* Assume recipient has a connection to the internet but it's not reliable, fast, etc.
* Assume recipient can't receive a download link
* Assume sender does not want to "send the file to the whole network" (I.e. BitTorrent)
* Assume sender does not want to dedicate server space to sending files.

At this point, I'm almost guessing you're talking about a series of ETH data transfer contracts.