This is what the cues are for, but setting them up for individuals to use was a real pain until Cubase iC (Pro) came along.
If you each have an Android (even a sub-$100) or iOS device (I don’t know if you can have a mixture), each can have a touch mixer (side-by-side vertical sliders for easy comparison, as shown on the product page) with all the sources (as set up in each source track) for one of the maximum of four cues on it.
The picture is for a tablet, but a phone will show only the mixer section. So if one of the performers is controlling the session, they are better off with a tablet, or a couple of phones with the cue mix on one and the transport controls on the other!
[CORRECTION 2014-08-02: Not mentioned on the product page, but to get the multi-section display, you will require an Android device with 8" (about) or larger display. 7" will show the ‘phone’ display. Just a little piece of info before you inadvertently waste your money.
Though I brought this information oversight to SB’s attention over a week ago, the page has NOT been updated. Thanks for giving your customers the info required for making purchasing decisions, SB - NOT!]
Makes it much easier than the fiddly horizontal ones in the standard mixers.
The actual outputs used for each cue will need to be assigned in your VST Connections dialog, and you may need a headphone amp for each performer to drive their phones.