E5 (Em?), G, C, A, D, E5... are the chords to mostly the entire song until the outro sticks to D5, C5, D5 to the end. My question is: what is the key center? Assuming E5 is a stand-in for Em, we have the following options:

E: i III VI IV bVII i... or i III VI V/bVII bVII G: vi I IV ii V vi... or vi I IV V/V V C: iii V I VI II iii... or iii V I V/ii II A: v bVII bIII I IV v... D: ii IV bVII V I...

I am leaning toward G personally because it looks the most natural with Roman numeral analysis in mind. Thoughts?