Sometimes this approach requires the producer or performer to take a more analytical approach to the arrangements.
If you have one main guitar part, you may have to dissect it into multiple parts. This is not unlike what an orchestral composer would do when writing on the piano. We will apply this method to the acoustic guitar.
Double Track Main Guitars
If you have a main theme, try performing it twice by tracking one and then a duplicate and panning them hard left and right.
Capo at Twelfth Fret (Doubled)
Perform the same main theme only with a capo on the twelfth fret. This will add another octave to the part and will immediately sound more symphonic.
Various Chordal Inversions (Also Doubled)
If the main theme is played using simple open chords, try playing simplified chordal inversions of the same chord. You may choose to play them in a different position of the guitar neck. Sometimes just playing a chord on a different string will provide a distinction on the chord.
Try playing three note chords instead of the full chord.
Different Guitars Doubling the Originals
It is a very common practice to perform the same parts using different guitars, This can offer a distinguishable tone and character that can't be captured from just one instrument.
Perhaps the parts can be additionally performed on a 12-string guitar.
Alternate Figures
Sometimes playing a simple part over and over can make a huge difference. For instance, just playing a 1/4 note pattern on the first and second strings at the twelfth fret can create an interesting counterpoint over a simple G-C-D progression.