Only slightly familiar with Tails. Is there an option to save data permanently in Tails? Downloading the blockchain every time Tails boots would be very inconvenient.
Yes, Tails has an option to enable an encrypted persistent volume.
My understanding is Tails has an option for "persistent volume" ... in which case it should work. I have not tested it though yet and would certainly weaken some of its appeal.
In reference to TOR/I2P .. you can run the wallet on a normal PC and point the Proxy (Tor) or SAM Bridge (I2P) to the Tails device.
On a side note, I2P works best when it has been running for a few hours (preferably days) ... so your best bet is to have a dedicated device which runs the I2P router and pointing the SAM Bridge connection from the Shadow wallet to it .. a RPI would be perfect for this and support the I2P network.
I really like the idea of separation, therefore having everything Bitcoin / ShadowCash related on a different 'machine' sounds neat.
Yes, a RPI could be nice for running I2P 24/7. Additionally having the possibility to install ShadowCash on Tails could potentially help the project, especially with the market around the corner. Also the user don't have to configure / install I2P or Tor since Tails already provides both. But being able to install it on Tails offers another useful thing: One solid base OS, there lots of Tails users out there, which could also become ShadowCash users and there it could be easier to offer instructions on how to get it to work. I hope you get what I mean.