Hello
OK, then some more ideas.
For me, the question is not vestibule at all or not.
It's, does the vestibule work properly!

When is a vestibule nice to have and what does it?
The answer is rain.

If I'm camping alone in the desert, the best tent is a self standing inner tent with lots of mesh, no flysheet mounted, watching the stars.

But if it rains, the problem is can I open and exit the tent without getting rain inside the inner tent.
Many tents with a very small vestibule don't work good in rain, and I mean rain that comes with wind and 45° angle or less.

The best vestibule have tents with tunnel construction.
I can enter the vestibule and close the door behind me, undress the wet raingear and then enter the inner tent.

I don't see how to design a tent without a vestibule that works good in rain and bad weather.
If I see it right in your first picture, the entrance/side is just one wall?
How did it work in bad weather?

I have a MSR Hubba Hubba NX for travelling with my trike.
Works not to bad in rain and you can roll up the both sides where the entrance is.
Then it's close to your tent in your first picture.







Vestibule rolled up may work for your most important feature


If I travell with my bike, I don't care much for weight, the bike has to carry it and I can handle my bike loaded with all that I need to survive.

That's how a vestibule has to be!










sushi

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