Since all email sharing plugins for Gmail require being installed on both sides, I think we need a simpler escape from Forward Hell — «Better Forward», a plugin that would improve life for both the sender and the receiver whether it’s installed on either side or both.
Sender side. Every email gets a «share» button.
If you share your own message to more people, it effectively gets re–sent with original payload and expanded headers. The entry in Gmail gets additional names in To, Cc or Bcc, subtly marked to discern them from the original set.
If you share someone else’s message, it is forwarded almost as usual, but with original payload and headers attached in a multipart portion. Instead of creating a separate «sent» item in Gmail, the original entry gets additional names in a new Fwd field.
Receiver side. Certain heuristic is looking at inbox and adjusting messages that look like they’ve been wholly forwarded: headers are restored to the originals, while the Forwarder is moved to a new Fwd-By header. So messages forwarded to you look and feel like they’ve been originally sent to you (in addition to other addressees), but clearly marked as Forwarded
If the forwarded message contains a multipart portion from «Better Forward» on the sending side, the restoration process is more complete and reliable.