I can administrate project, I am not developer and you can't use only one developer for such project. Several developers for 3-6 months work would cost you much more than 2000 USD. I put price 15k USD approximately.
I am limited in writing here, 1200 characters, so, shortly, Intel and other shit companies are already subordinated to NSA, your OS would have to work with ARM architecture, not Intel. Intel included backdoors and other major companies have american nsa scientists and managers. But Hey, I don't trust even to Tor, I speak inside of frame of your understanding, in my understanding, as long as you don't have your own network of proxies than you relay on tor or i2p, you make mistake. and you can have such network only if you are rich. with 2K USD, no chance to make anonymity of users 100%. so, your needs are using tor network, my needs would be making your own network.
part of your needs are already made with whonix and i2p, users can run I2P inside the Whonix-Workstation: user -> Tor -> i2p
in theory, tor provide user with anonymity, and i2p give them possibility of "archive". whonix can be installed also with full disk encryption.
as I said, arm architecture (hardware) is not under control of NSA. but beside hardware, you need and Internet independent from NSA. ops, only 200 characters left, the end of writing...