Kylo Ren is necessary FOR HASBRO. And for the retailers. Why? Because he sells through. He has sold through on refresh case after refresh case of third tier characters. And he probably will in this instance, too.
Hasbro is not going to blow their ROGUE ONE load on a single wave of figures. Especially since the ROGUE ONE line launch will no doubt feature more than a single wave of 3.75" Basic Figures. The launch will probably consist of at least 2 waves of basic figures, 1 wave of deluxe figures, 1 wave of 6" figures, and 1 wave each of Class I, II and III vehicles.
Actually, I think there will only be one 3.75" 5POA wave at launch. There was a lot of confusion with retailers regarding Jungle/Space/Desert/Snow assortments which was further complicated when not enough product hit stores for the Force Friday launch and managers arbitrarily starting limiting how many of each assortment you could buy.
I think the retailers would want the launch to be as simple as possible which means 1 case of each item type.
Based on the character list of Rogue One, there are a lot more than four characters in Rogue One, especially since the first wave appears to have just Jyn, K2S0, Stormtrooper & Deathtrooper - that leaves plenty of Rogue One characters for Hasbro to put in future assortments - I hardly see how those four figures is Hasbro "blowing their Rogue One load".
The inclusion of Kylo Ren - throws the case off packing ratio wise, which is a frustration more than anything else. A nice 2x pack-out would mean that you could order from EE or JTA and skip the nonsense of Force Friday. He also doesn't sell out, in the local stores around me, there was regularly 5POA Kylo re-releases from the PZ / Goss wave and I'm pretty sure I could walk into at least one of my local WMs right now and score the 3.75" TBS exclusive Kylo Ren. He was done to death and the only version anyone is interested in is the one with his helmet off. If a Kylo Ren absolutely had to be in there, a battle damaged version from during the fight with Rey would have made much more sense.