JimB on the tilt front you could have two positions Winter---Summer but with just three positions you could have Winter----Spring/Autumn----Summer.
The reflector is a very good idea and, who knows, it might be possible to take advantage of reflective objects in the landscape e.g. sea or other body of water.
Reflectors are not as much fun as heliostats though, imagine three or four following the sun and focusing on the panels.
I have been reading and the efficiency of PV panels does fall with temperature, the losses can be high. Trying to keep the panels cool makes sense.
Ideas might be convection, a heat sink, maybe evaporative cooling. Pumping water for cooling probably does not make sense as it might be better just to buy another panel, but any free flowing water could be used.
Another big saving is keeping the panels clean. So some detector for when the panels need a wash might be worthwhile.