What Fantasy JRPGs don't have is offensive Polymorph Effects that last forever, Characters creating their own demiplanes and manipulating reality and time there, summoning demons or angels to aid them on quests for long periods of time, players raising platoons of demons or undead (using class abilities, not GM plot), or "City Nuke" shenanigans. Even routine access to personal flight is usually quite limited (you see hover effects fairly often). From the player's capabilities in a JRPG, other than the numbers (which allow RPG characters to eventually take on creatures that in D&D are up to CR20); they don't get effects beyond 4th level wizard spells, and don't even get full access to spells up to 4th.
Yes they are, yes they do, yes they do, etc. Airships, demiplanes, summoned angels, all that kind of stuff shows up in the PCs hands. Further, they fight robots and giant plant monsters and enormous dinosaur-demon things by the first third of the game, things which register as CR 10 or better when you face a version in Pathfinder. Power-wise, it's a completely different animal with the JRPG being higher. The only things they don't have are effects that operate off-the-rails or outside the box. JRPG character with her demiplane uses it to heal folks, and one time lets 'em hide out in it when the city gets nuked or whatever. This isn't "higher power" when a PF character does it, it's just another function of PF having more options (because it isn't basically a novel) and letting you use lateral thinking to get around problems you would otherwise have to plow through.
And once again, you're talking A DRAGON, the critter that's supposed to be the end boss (traditionally speaking). JRPGs do that stuff all the time, D&D that's like taking ECL +18 (remember, it's different than CR for PCs, for good reason) and stacking on 10 levels of fighter.
An Actual Large-Size Green Dragon is only CR 8; which is a far cry from CR 20; though actual dragon stats are not particularly relevant.
They are very relevant. Giving the fighter natural reach and stackable natural armor is a big deal. It's why CR 1 critters were listed as ECL +3 (give or take) back when they still did ECL.
What I'm Describing isn't "Dragon Statblock + Martial Stuff". What I'm describing is Martial Character + "Miscellaneous Variety of Short-Term Dragon-Themed Metamorphosis Buff Effects...
That's very different from what you first described AND what you were dismissing previous builds over. I mean, what abilities do you want? And how much are you willing to sacrifice to get them? Ryu usually was one of the weaker fighters of his little gang, he just had the trump card superpower he could whip out.
Start as a half-dragon, run some Mutation Warrior, fake the other abilities with a few sorceror spells.
Or go Beastmorph alchemist, rolling into Master Chymist (which straight-up has a "dragon morph" mutagen) for a total +17 BAB at level 20. You are "Dragon" subtype, (because half-dragon) and you get most of the abilities. You may not have a fear aura, though there are ways to fake that too if you hunt around for 'em.
"It's not perfect!" you say? Well you're asking for a cross-genre bit of power creep with a very specific focus and very specific magical abilities. We fake it. What you REALLY want is a custom class of fighter that trades a bunch of fighter abilities for a very specific spell-like ability. Nothing wrong with such a homebrewing, but in lieu of that bit of hard-to-balance creativity, the above gets pretty close. It still won't be BoF dragons, since the dragons are just plain different in Pathfinder, and how much variety you get in your transformations depends on how much "martial" you want to sacrifice (and if memory serves Ryu often didn't get a lot of variety in his draconic abilities).
And you can be Grey Mouser just fine, the problem is Grey Mouser had the glorious magic of "author fiat" making his d20 rolls for him. Same issue as Sherlock Holmes, really.