I had a thought today. It would make sense to introduce Jake now, and have the character go through a modified version of what happens to him in Gunslinger. Then move on to movie 2 with Susannah and Eddie, and loop back to him in movie 3 as an older version of Jake (because the actor is going to age), or even a new actor at the same age as a Jake from another Level of the Tower (other worlds than these). That would make more sense to get all the Gunslinger and Wastelands Jake out of the way before getting to Eddie and Susannah.

Spoiler:
What if in this turn of the wheel, Roland remembers Jake and what happens with him, and knows that TMB and CK are going after him before Roland finds him to use as a breaker? Roland knows this, he's got the horn after all, and we've seen that he CAN remember snippits from one cycle to another. What if this time he remembers a bit of Jake? So he's searching for a door to get to NY to get to Jake before TMB can get him as a breaker? Kinda like that. Then that would explain bringing in Pimili and the other low people and the Tirana chick, etc, so early. Roland saves him from TMB but still sacrifices him in order to get more info from TMB. Movie ends with Jake dying, Roland moving on to drawing Eddie and Susannah and maybe Jake again in movie 2?