Well, I'm not sure about that. Your points make sense, but at the same time it seems odd to me to simply call an animal "hybrid" although it's based heavily upon a wide base of creatures that really existed; dinosaurs.
Odd, maybe, but words are important and you hardly can clasify the Indoraptor and the like as regular dinosaurs. We don't even know if they actually sport all the anatomically clasifying characteristics, but if JP/JW were real, chances are more definying traits outside of skeletons would have been discovered, and I'm pretty sure they might not have them all, seeing their unnatural intelligence and kill-oriented behaviour.
Anyway, regular taxonomy already sets them appart, quite rightly, as new, different species but taxonony has already it's problems and limits for debates on what makes a new species "new" are sometimes heated and endless. And those issues became bigger and harder with natural hybrids. And we are speaking of lab-made-up hybrids here.
Well, the point about adding the hybrids and leaving out Mosa and Pteranodons is that Frontier developed animations and mechanics for dinosaurs/creatures that are either bipedal or even quadrupedal, so both the Indominus rex and the Indoraptor fit in there. Implementing the Pteranodons and the Mosasaurus would've required completely new, unique animations and mechanics. More effort and work for the developers. I believe it's simple as that.
I understand that. However, that's no good reason at all for completely excluding both from a game based on Jurassic World. You can't have Jurassic World without Mosasaur and Pterosaurs at the very least. Hell, the later were even canon attractions since JP!
Of course, I'm aware those would mean more work from developers but I'd think no one is asking for marine or avian animals for free. I am certainly neither wanting nor expecting it, but I simply refuse to pay for things such as Ankylodocus or that other freak pal with canditates much more requested and suitable already on the source's canon.
Oh, and regarding the Mosa: In my opinion she is just the waterborne copy of Rexy. Yes, she did serve a purpose in JW, but scrap all her appereances in FK, it wouldn't change the plot in the slightest. Just less many eye-catching scenes, that's it. I'd classify her as a badass, but useless character without much immersion and necessity to be part of the movie.
Maybe you're right but, still, they are part of JW. So, again, why Ankylodocus or whatever made-up godzilla and not more movie-characters?
Anyway, about the point of not having so much impact in the plot, I disagree: the concept of "Jurassic World" dramatically expanded itself with Dr. Malcolm's words after the animals scaped into the mainland. I think the portraying of both flying and marine reptiles was done not only out of settings' needs (any competent zoo would have made to expand their species roster beyond the usual ones, particularly if they needed to increase public interest from time to time: Indominus wouldn't have even existed if both air and marine "barriers" weren't already reached on the cloning tech) but also to stress the sudden paradigm-change for humanity. JW3 will, I think, be all about that: it is a truly Jurassic World when prehistoric animals can be found on air, land and sea. There is no more "safe places" on Earth anymore.