From the white paper:
" VII. When reserving takes place it is broadcasted to the network, so offline block generation is possible by other peers, no need for keeping the wallet online to get the return. A generated block will be signed by other peers. Example of offline block generating: A puts in reserve X amount, and the reserving is brodcast to B, C, D, E, F, G, H, J peers. D generates a block for A, that is accepted only if B, C, E, F, G, H signs the transaction as valid. "
I am not so sure if i am getting this right, but it sounds like this proposed system is a brain wallet. Isn't POS is a system where a block is created every x amount of time. IN NXT, a block is created every 60 secs, therefore 1440 blocks per day.