Sure that is in fact a very good chord substitution in G Major
If you take a G Major 7 Arpeggio you have most of what's in the F#sus 4 except whats in the F# sus4 chord contains all the hippest notes you can play over a G Major 7 th chord / tonality
G Major arpeggio starting on the 7 th scale degree = F# G B D F# G B D F# G
F # sus4 arpeggio ( eliminating the 3 rd scale degree ) starting on the 7 th scale degree = E F# B C# E F# A
With the F#sus4 , what you have is a form of a pentatonic scale once you add the A note .
All the notes in that scale are excellent because they introduce the upper harmonic content of the tonality itself when played over G
example F# = Major 7 th of G . A = 9 th of G , B = 3rd of G , C# = the +4 of G , E = the 6 or 13 th of G , F# = the Major 7 th of G , rinse and repeat ...
The Logic behind the B Minor is also considered a nice jumping off point in G since the B minor chord is so closely related to G Major . In Jazz when people play Standards they often will substitute a Minor chord a Major third above a Major 7 th chord ...The B Minor triad contains the third , the 5 th and the Major 7 th of a G Major 7 th chord
When playing a B Minor 7th chord over a G Major 7 th chord, the A which is the flatted 7 th of B Minor turns out to be the 9 th of a G Major 7 th chord ...all arel very choice notes to play over a G Major chord
The advantage of the F# sus 4 while in G is it introduces the C # ..This G major now becomes a Lydian type of sound and and tonality the +4 C# is a very expressive note choice over G Major and it it is much preferable to using the fourth scale degree in G which = C ..
IMHO C# and D sounds way better than ever playing a C note over a G Major Chord ...
Also the F # sus 4 make a nice 5 chord tension cadence when played just before a B minor in G ...
I'm still having my coffee so my explanation could have been better written
Oh well you get what you get
Kenny