Over the last few years, I've seen a few combo panels around,
but since they are integrated into one unit, they aren't a big seller..
#1. After the company fails, you are stuck with a combo panel you can't repair. (no parts).
#2. Combo panels are costly. It might be cheaper to install two systems.
#3. Complexity means more things to go wrong.
Since the back side of my PV is hotter than the sunny side, I've wondered about cooling them,
by attaching a DIY hot water heat exchanger under the panels.
Seems like a lot of work to attach the HX units to each panel,
when I could build HW panels (or buy used HW panels) for a little more $$.
The complexity builds up if you live where it gets below 32F..
Now you need anti-freeze water, instead of tap water.
That means a double-wall HX (to meet code).
One other problem with using a closed loop system. When the storage tank water gets really hot,
Then fairly hot water is going to be pumped into the HX.
That's going to mean the PV is not going to see a lot of cooling.
So, the big PV cooling gain might not be there..
(Unless you use a bunch of hot water)..
IMHO, Not really feasible for the average DIYer..
One of the best ways to get more power out of your PV is to cut down all the trees that shade your panels..
Another way to get more juice is to make your elevation adjustable.
So you can tweak the angle to match the season..
I don't recommend a DIY solar tracker, unless you keep the PV under 500w.
Gets too complicated with big arrays..