Regardless of what tack the screenwriters take they will have to invent a great deal of material, and I see no reason to think they wouldn't do so with a Young Aragorn series in order to flesh out the information in the Appendices with character arcs and a greater supporting cast.
Sure, a great deal of material will have to be invented by the screenwriters either way but the problem with the Young Aragorn arc can be put plainly as follows: it doesn't and quite simply cannot, by its very nature (if they are to remain even moderately faithful to the events of the books and films), amount to anything epic or grandiose in scale to rival the LoTR films or GoT.
It essentially ends with the Hunt for Smeagol, and this is barely (if at all) connected to Aragorn's earlier errands like his raid on the Corsairs of under Echthelion. You aren't going to see Aragorn crowned, because that happens in LoTR, for instance.
Young Aragorn is obviously a prequel to Aragorn's plot in LOTR of growing into becoming the restored King of Gondor but it doesn't really function well as a true prequel to LOTR itself, in my opinion, in the same way that a Last Alliance storyline would (by ending where the prologue in the films and the assumed back story to the novels, filled in especially by an info-dump from Elrond in Fellowship, begins).
According to the Appendices Aragorn spent little time in Eriador, period. It's doubtful he had much of anything to do with the protection of the Shire since his main purpose was "labour[ing] in the cause against Sauron", both in the service of Rohan and Gondor, and later traveling "alone far into the East and deep into the South, exploring the hearts of Men, both evil and good, and uncovering the plots and devices of the servants of Sauron."
I should note, I was being deliberately facetious with that comment
Naturally, I don't reasonably expect a Young Aragorn TV series would be concerned with him "strolling around the hills of the Shire" sucking berries and hanging out with the Hobbits.
And as Otaku said, I started this thread without taking into consideration the full ambit of Aragorn's travels and I thank the good people here for clarifying aspects of this, as you do above. However, I still don't see the epic potential in the coming-of-age, chivalrous errantries of Aragorn as Thorongil.
I mean, honestly, does it really amount to a grand narrative worthy of a five-season extravaganza to rival the LoTR films/GOT and a fortune equivalent to a small country's GDP?
(This post was edited by Althoun on Apr 20, 9:51pm)