Here's my take on it. As far as the EV/JBL mix goes. I think the BE will freak if he walks in and sees different model and make cabinets stacked together for FOH. A way around this would be to use the EV's for the mains and the JBL's for some delay towers. While this arrangement may not be rider friendly, it is a much easier pill to swallow than having a mismatched set of mains...
Also, consider the monitor situation. These older classic rock bands are hard on monitors. They are usually quite deaf at this point in their carreer. If you can't provide some absolutely stupid loud wedges and sidefills, consider renting a monitor rig. I'm not kidding here. We're talking painfully loud wedges for these acts.
HTH....