Launcher Vault download optimisation

After 4.10 update I’ve finally considered to make this post.
Download manager in launcher is very ineffective (but fast)

This is KiteDemo comparison table, each folder is about 24.8Gb in size, 13.3Gb are different from folder to folder.
It’s 11.5Gb of same content per each version. AFAIK, traffic from amazon s3 ain’t free, i.e. 1000 downloads will cost You additional ~$300 (100011,5Gb0.0275$/Gb) for only one asset (largest, but still). Plus, not all the users have a 100M Internet connection.
If You just implement even a basic script that will copy (or move, personally I don’t need 25x3=75Gb of project files) files from existing project based on diff table (it is permanent!), it will save YOUR money (ofc in case it’s not implemented yet).

p.s.: also please consider to add a BitTorrent protocol, that may save You much more (some AAA publishers using one in their launchers)

I like the idea of pre-downloaded content from other engine versions transferring over to new engine versions without re-downloading, especially if it hasn’t changed. However, it would have to go through some kind of verification for that to work, which involves uploading or downloading something.

BitTorrent just opens you up to piracy straight away (mind you, that’s always been and always will be an issue regardless). A lot of studios (mine included) actually block that kind of activity anyway to cover their own backs, so it should still be optional.

Ofc it should be optional, since BitTorrent requires an open port for incoming connections. But BitTorrent is much safer protocol than most people think of it. Without peer exchange, local peer discovery, DHT, and with private tracker You could distribute free/learning content without any risk.
There are several open source projects, and some of them are libraries on c++ or c#.
Well, it’s not the topic of this thread.