Yes, I understand why you started your conjecture, amysrevenge, but I agree that it's not exactly a Season 4 question! (glances at thread title)
Personally, I am *exceedingly* hesitant to go the 'tell Tuor and Túrin's stories in parallel' route, because I think that there will be too much temptation to sacrifice some of the story in service to creating those parallels. Making them the same age is an example of that; they're not the same age, so if we changed that, we'd have to give them a shared childhood. Their fathers are extremely close brothers, and they live in the same place, so they'd be...what you might expect of close cousins. And then there would be the obligatory scene where they, as young kids, discuss the future, and both of them say something that later becomes ironic or poignant, and just...
I don't mind inventing scenes. I wrote a brief scene for this project where Galadriel and Aredhel hang out with toddler Idril and have the 'you can't marry your cousin!' conversation, which is exactly the sort of 'this will be significant later' kind of scene I'm talking about here. The issue isn't that this ruins the story, but that it puts...false pressure...on the story to have the characters conform to some sort of opposite foil thing which will (eventually) dictate how we tell that story.
There are parallels that are significant and could work really well - Tuor/Idril vs Túrin/Finduilas, for example, with Gwindor and Maeglin as the other side of the love triangle. Tuor being raised by Annael while Túrin is raised by Thingol. Etc. Tolkien definitely considered these stories tied together, and it wouldn't be wrong of us to interweave them. But. If we tried to make *every* episode of one season a Tuor & Túrin story, where their entire story is told in parallel? Well...that would be very challenging to do well, and would require some really good planning. Not saying we can't do it...just that we'd need to put a lot of up-front work into it to make it turn out *well* - to find the ways to interweave the story that feel almost natural, rather than forced or cliched or obvious or, whelp, guess we have to do it this way now.
But, hey, we have time, so if someone wants to try to map out a Tuor&Túrin season with interwoven episodes, knock yourself out!