Your right it can convert to air tight with little issues. I like how it came out and the design you made. Nice job

But it won't be very hard to make it airtight if needed

Yes I saw that, if you have a radiation storm, or too hot or too cold, or any other bad thing happening, you'll kill all your plants. So only good on earth-like planets with fair weather

I seem to vary from base on planet to one in space. I use this base on planets with Oxygen since where the grow plots are is not a air tight area.

You're right. I'm generally not on an earth-like planet :-P

I usually try to put a massive garden in my base just so I can make emergency packs fast with just a few picks of the garden. That is if you looked in the underground section there are a TON of fuel tanks to ensure the power never goes off. Also only use the base on a planet with oxygen so if by some evil chance power does go off the plants do not die :)

Nice job :-)
Just one thing I prefer not to do, is to put the farm on my base. I prefer another building, so that I can shut down the main base when I go roaming in the galaxy, to spare the fuel, and just keep the farm set on ;-)