No, I've never tried to take a western style room and turn it into a Japanese one. I can never satisfy myself as to the results. But I do wish you luck. Send pictures when you get it finsihed.
I think western rooms lend themselves towards Chinese styles more than Japanese (unless you are willing to take down walls and redo the size of your windows). But faced with a blank slate, western-style room, I would probably go for a colonial or georgian. IMHO these share a lot with Japanese styles; clean lines, objects being functional and beautiful (none of this bauhouse nonsense). But what do I know, this is only a hobby...