As far as the panel height, Citations, King Airs and the Premier have vertically adjusting pilot seats.

Aero550 is totally right about the 500 series being HOT in the summer. I have always found the King Air to be comfortable. All but a half hour of my Premier time is in the sim so far, so I don't know about it's temperatures, but I can tell you it has dual zone cockpit/cabin temperature controls, and has the most powerful blowers I have seen. I don't anticipate it being a problem.

Once you get to altitude, it is not as big of a problem.