Sounds good!

BTW, JP, I was thinking more of the diminished chord than the major 7th as "jazzing it up."  You're using a diminished where I use a minor 7th.

FWIW, here is what I have been playing:

(G) All of me,
 Why not take (B7) all of me? *
 (E) Can't you see (E7), I'm no good,
 Without (Am) you ?(Am7)
 (B7) Take my  lips,*
 I want to (Em) lose them ;(Em7),
 (A7)Take my arms, I'll never  use (D) them.(D7)

 (G) Your goodbye
 Left me with (B7) eyes that cry.*
 (E) How can I(E7), go on dear without (Am) you? (Am7)
 (C)(Cmaj7) You took the (Am7*) (G dim) part
 that (G) once (Bm) was my (E7) heart,
 So (Am7) why not take (D7) all of (G)me? (E7).
 So (Am7) why not take (D) all (D7) of (G)me(Cm - G  ).
 

*I do a thingy with the B7, where my index finger alternates between the E and the A string from beat to beat, so I don't change chords (other than that).

The red chords are where I would substitute ones that you've suggested.  (It sounds better to me that way.)  I don't use Gmaj 7 because it's a gawdawful contorted hand position for me.  (If I want to use the major 7th, I'll  play it in C.)  But personally, I think the song sounds better with the major chord on the first line, rather than the major 7th.  Just my taste--I play an upbeat version of the song, anyway (first time moderate tempo, second time through much faster).
 

I offer my version only as one option.   Play whatever sounds good to you, Mudlark!

BTW, Sorcha,
Although this song is not "folk," it has been done in many different arrangements, tempos, etc., with modifications of the tune and, no doubt, chords, too.  I've heard so many versions, I'm not sure which one is the original.   The "folk process" happens with other genres, too!

Genie