Hmm, a re-establishment of Erebor frame could work for this season.
We do want to get a Bilbo-centric frame at *some* point to introduce hobbits more fully, but we could certainly do that for Season 5 with the introduction of Men. We can't come back to Aragorn or Arwen until Season 6 (the Beren/Lúthien season), I don't think, so we need one non-hobbit suggestion, anyway. And Trish *has* suggested a Thranduil/Woodland Realm-based Frame narrative. So, this is good.
As for the frames being chronological - roughly speaking, yes. They should happen in order. Or, at the very least, they should be *able* to happen in order, so that there is no need to explain to the audience that this part of the frame is earlier than this other part of the frame that they've already seen. So...vague, unspecified timeframes are an acceptable alternative, so long as we're not jumping ahead or jumping back.
So, the 'Sam and Ted Sandyman' idea has to be nixed - we can't jump that far ahead in the Frame at this time without causing major confusion later. If we go to the Shire right now, it will be Bilbo we see there.
But we could certainly start in Erebor right after the Battle of Five Armies and wind up in the correct time frame by the end of the Season. For reference:
In the Season 1 Frame, Aragorn is 10 years old.
In the Season 2 Frame, we're in Lothlorien, so it *could* happen over a wide range of times, but we do try to set it right after the Hobbit when Gollum is loose.
In the Season 3 Frame, Aragorn is 16 years old.
In the Season 6 Frame, Aragorn will be 20 years old.
So, if our Season 4 Frame is 'a few years later' from the Battle of Five Armies, we're in good shape. We should probably intentionally put it at 7 or 8 years later, but...that's the general idea.