Japan is such a nice country because it is a homogeneous country, with one ethnicity and one culture. Even if you bring in people who are worthy, let alone if the bar is so low as 'not a criminal', you are going to lose that.

Europe tried this (I am an immigrant myself), and we've had no end of trouble because of it, and we're having to spend vast sums on immigrant criminality (mostly second and third generation, so "not a criminal" does not work there) and benefits - which if spent on the domestic birth rate, could actually have done a great amount of good - if with an 18 year delay.

It's not worth it.