I am just quoting from the PROs...
Do what you want, after all it is your grow... but if you research and talk to some experienced growers... you will see that I am right...
Plenty of people do the wrong thing everyday, thinking they are correct...
What happens when your temperature has reached the "cool point" and your exhaust needs to shut off??? do you also shut off the ventilation to your cool tube? what happens then to the plants that are so close to the light because of that ventilation???
Sounds like a nightmare to me....
keeping them together is inviting the possibility of temperature fluctuations beyond what you want...
I want a good stable environment for my grow, and keeping it separate is the easiest way to achieve that...
But then again, I see people driving with flat tires or out of gas all the time.. so...
go with what you know....
Best of luck to us all...