The revelation "that they're also tossed around the possibility of introducing plot points in Agent Carter that pay off later on Agents of SHIELD" is not really a surprise at all.
My theory on this show has always been that it will act as the "answer" to some mystery that AoS will be investigating. They play it out all the way up to the mid-season cliffhanger of AoS and end on a "hey we just found this central stockpile of information that that answers the riddle..." and the camera zooms on a file marked as written by Carter, or they roll a piece of vintage film acting as a log entry by Carter, or something along those lines.
Carter runs... tells a full story, leave some questions unanswered that tie heavily to the AoS plot and when AoS return, fans have a good idea where they might be going next.
I would also not be at all surprised if a younger version of Lucy Lawless's character will be somehow relevant to the Agent Carter series. "Let me tell you about this thing that happened when I was younger..." sort of thing.
If I'm wrong about the method, they still have endless ways to accomplish the same objective.
