G Chord Progressions: Relative Minor Substitutions

Remember from last time:

I. G major
ii. Am
iii. Bm
IV. C major
V. D major
vi. Em
vii(b5). F#dim

Each major chord in the key of G has a relative minor that might sound great instead of playing the major chord, and vice versa. What? In other words...

I/vi: G major could possibly be substituted with Em
IV/ii: C major could possibly be substituted with Am
V/iii: D major could possibly be substituted with Bm

Instead of playing I-V-IV-I, for instance, try the following permutations (not an exhaustive list), but we'll start with the original progression:

I-V-IV-I: G D C G
I-iii-IV-vi: G Bm C Em
I-V-ii-I: G D Am G
vi-V-IV-I: Em D C G
vi-iii-ii-vi: Em Bm Am Em
etc.

Substituting a major chord with its relative minor (and vice versa) might liven up a boring progression with a less boring progression (albeit still widely used).