In germany it doesnt matter on wich side the steering wheel is. Only the lights need to suit the country if they have a unsemetrical pattern. But that shouldnt be a big deal.
How long the VIN is doesnt matter.
In addition to that you have to make certificates for the exhaust emission level, the noise, the power output, the highspeed etc.
Especially the exhaust emissions can be hard and expensive because you have to fulfill the euro-norm wich was effective when the car was build.
I am not sure, but I think the Tüv has an archive for all aproved vehicles. But so far I don't know if a JDM STi is aproved this way in germany. And if there is such an archive it has to be exact the same car-model. There are a few STI floating around, but they are either way "half-legal" or they belonged british or japanese people who moved to germany and registered them this way.
I know there is one 22B in germany registered this way. The owner is on this forum, but he keeps quit