New Chords!

I'm shying away, it's my signature move...

Today I learned how to play a song my roommate wrote.
It's a beautiful piece, and uses chords I haven't used long enough to have memorized.
they're:

Bmin7 - 232x2x
A7 - 02020x

Used in combination with Em (000220), D (2320xx), and a form of G (xx0023) it's a great piece.
The verse is D-Em-Bm7-Em.

He's taught me much already, not only how to write good lyrics through example, but now I know how to use min7 chords wherever I want.
They replace the IV in a I-IV-V, and the key of the min7 is a note in the I chord.
I-IV-V is G-D-C, and G is made of G+B+D, so I replace G-D-C chords with G-Bmin7-C.
In D-G-A, I can use D-G-Amin7, too for example.