I don't know the music, but what I would do is use the synths texturally, and possibly build the electronic sounds out of the acoustic guitar noises. You could probably build some pretty decent beats from the squeaks of strings and a few hammer-ons. Acoustic guitar sounds can also be manipulated into this lovely singing noise if you put a really hellish amount of echo on them. In any eventuality, I think they key will probably be to match your electronic sounds to the feeling of the guys music. If it's bright and airy, use lots of lap-pop style pops and clicks and maybe a bit of very subtle 909. Try and keep everything very clean and whatnot. If the musics more sort of dingey and durgey, go the opposite, lots of textural sound, deep kick drums, maybe a bit of noise.
Actually, a bit of noise is always good.
Although probably not what you're after, my suggestions for bands that accomplish this well would probably be Ostara, Of The Wand and the Moon, some Sol Invictus, Hide and Seek and Current 93. Odd dribs and drabs of Coil as well.