> 2) Why would you need a One-Pass Signature Packet if we conform to 10.2
and simply prepend a normal signature packet to the literal data with a
> subpacket of type 16 (key id), thus removing the need for a One-Pass
packet
> in the first place?
This is so that the signer can process the message in one pass.
He doesn't know the hash until he comes to the end of the message,
so he can't compute the signature until that time. With the old-style
signature packets he would then have to go back to the beginning of the
message and put the sig there, preventing one-pass processing.