Project Nippon

...My friend Rob... that's where you're compromising the most actually.
The frame should be your least of worries.
Frames come and go. You can crash it, brake it, get it nicked...etc...
Want a piece of advice: Get yourself quality components, good wheelset, if you so like Japanes...
Peace.

This makes no sense, if you get your frame nicked, unless it's from your house it will be the entire bike with the components, so this makes the component bit a bit redundant, the changing frame bit makes sense.

Keirin frames are perfectly strong, ask Build or Ma3k, both have keirin frames and don't treat them extra carefully, and I believe they are both still ok, they were made to be extra strong so they can survive crashes and not break.

Thirdly if you want to do a japanese build you will need a japanese frame, otherwise it will be pointless trying to make sure that the rest is japanese.

Why not just try to build a classic looking steel lugged style bike, still has a theme just seems to be more attainable on a budget.