It's the sentiment you're going to continue to hear from experienced keepers. Many of us were in this hobby LONG before these forums even existed. So we did play around with things and through trial and error we learned.
It seems to me you just want people to be echo chambers for what you want to hear. Not gonna happen, not from experienced keepers who put the animals first. There are enclosures on the market, readily available, designed SPECIFICALLY for snakes, some even built with arboreal or semi arboreal needs already accounted for.
The doorway excuse sounds pretty flimsy too. We all have doorways. I'm guessing yours aren't a whole lot smaller than everyone else's, if not standard size.
Some enclosures come modular so that eliminates that problem.
As for grow tents, the walls aren't sturdy, the zipper isn't secure, I don't know specifics about heating, so I won't touch there, and saving money isn't a good excuse.
When you buy an animal you take on the responsibility of caring for it for life. That means planning ahead. That means taking proper equipment and enclosures into consideration before bringing the animal home. Since you already have the animal it's up to you which way you go.
Your snake, do what you want. You can choose to do it right, or not.