You can mix and match the sound files into a new profile but i found it easier to use a profile switch, (supplied with the voice pack) this gives you other voices when used with other voice packs. I have twelve or thirteen voice packs and have used multiple profiles in their basic form to simulate crew. However, I have returned to using just one voice, Kate Russell (Kate profile not Doris), One voice profile can be customised a lot quicker than multiple. I may use the others over time for variety.
If you do choose to get other voice packs to edit together, use copies of the voice packs for your editing purposes not the originals or you may end up with a real mess and no original to fall back on.