If the electric guitar with distortion effects is added with a certain "flavour" (cab simulations, mic simulations, room simulations) and has a specific frequency range for presence, it will not interfere with Vocaloid. Also the Vocaloid sound must be found the proper presence frequency too.
To me it was easier than I thought after I emulated the amp+cabinet+size of speaker+ room size + mic types and distances. Before I had Montage8 I was using GuitarRig5 and Amplitube3, now it's all in Montage8