Key to curing paint are two factors, time and airflow. Air caries away the solvents and allows more to escape. Time allows the process to happen. Spray a guitar keep it in a vaum the paint will never cure.
For heat.
One option I use lights not pointed at the body to heat the air and raise the ambient temperature. I do this so that I don't heat the paint directly and cause it to skin over and trap the solvents beneath the skin and never cure. I just leave them on all the time, but my cold weather is 50 or so in the garage. The lights keep my booth between 70 and 80.
The other option is to use less toxic paints, if you can get over the marketing, internet, and cool guy hype about nitro. Many woodworking finishes can be brushed on well, so the fumes are even more reduced.
About your idea.
The window up top has 2 issues as I see them. One is your dragging fresh air over your paint, unfiltered your gonna get junk in it. I have a great flake job that has a piece of lint in it because my filtration sucked at the time. The other is that air is going to be cold.
If your going to go forward with a booth I would build a stand alone box with intake and output filtration. Use piping to vent the booth out your window. I bought my filters off ebay they are mad for pro booths, I use an intake, overspray and carbon filter.
I'm still reworking my design and will totally rebuild after my electrician rewires the garage.
Take some time and think about safety, grounding, overspray control etc...
I'm trying to switch to entirely water based paints but will keep a booth to control my painting enviorment clean and surrounding areas overspray free.