correct me if i'm wrong, but i believe Gsus4 is GCD. C is the perfect fourth of G and C# is the diminished 5th. if the song was in the key of Ab... an argument could be made that is chord is Gdim (G Bb Db), however, that doesn't account for the D note. there's not D in the key of Ab.
in my experience, though that doesn't mean much, if 2 notes are right next to each other it is best to assume the lower note is the Major 7th of the higher... ie if D is the root then C# is the Major seventh. the best i could come up with is DMaj7add11 (D F# A C# G... with no 3rd or 5th) where G is the 11th. though this doesn't quit fit into the key of G either. a more appropriate chord for the key of G is D7add11 (dominant 7th D F# A C G) but then that would make the chord a Gsus4
. DMaj7add11 does work in the key of D but then the B would be Bminor..... but i guess that's why it's called "Theory". breaking the key is fun
Since 0234 is G D G C#, you've doubled up the G notes. see how 0254 (G D A C#) sounds. this would be a DMaj7add11 with no 3rd.
either way my vote is for DMaj7add11
lol