Several larger US companies are using well under 30 denier PU coated nylon: MH and GL to name two. Yah, I know - it costs more.
Re the vestibules:
"1. Vestibules place gear in the doorway, where you have to crawl open it to get in and out of the tent"
A straw man. Well designed vestibules are large enough to hold the gear under the covered and closed side, leaving plenty of space for entry and exit on the side that opens. Another vestibule at the rear of the tent can also be used. My modified One Planet Goondie holds enough under the fixed side of the cover up front, that the vestibule under the rear cover was replaced with more floor space. BTW, the fly is 15 denier PU coated nylon, trail weight & guys < 2.5 lbs, floor area > 23.5 sf.
"2. You have to open two doors every time you want to get in or out"
If the tent has a canopy or fly, it must be opened to get in or out. If you also want bug protection, a netting door must also be opened. That's par for the course.
"3. Generally, they inhibit ventilation when deployed for poor weather. It is true that some vestibules do allow you to keep them open in the rain, with an otherwise positive drip line, but this is almost never the case."
It may be almost never the case among the larger US companies. But among the better tentmakers, it is almost always the case. Vestibules are not the issue. Competent tentmaking is the issue. Have you looked at the TarpTents?
"4. When closed for weather protection, ventilation is USUALLY reduced dramatically, and I can't think of a single design that allows you to continue to look outside and enjoy the views, regardless of weather. I have hiked a LOT in the rain, and being cooped up in a steamy tent without air or a window is not fun, especially when you can have all this while going even lighter."
If this is an argument for tarps, please say so. They definitely have their place. As for tents, you must button up in high winds else the canopy or fly will balloon, be subjected to great stress, and place the anchoring at risk. So the answer to steamy is good vent design, or in the alternative, awnings that allow the wind to pass right through, which is problematic because rain may be coming right along with it, and gusts can be totally unpredictable. I camped in a modified two-awning WE Bug Dome for several years, and greatly enjoyed the full view out the front and cooking and eating under the front awning in the pouring rain. But wouldn't dream of taking it well above timberline in exposed locations.
The tent weighs 3 lbs complete, in the bags, and the floor area is 30 sf.
"5. You can absolutely use the doorway of a awning/door combo to transition from wet hiking to dry camping. In fact it is one of the main benefits. ... . The drop door is used to sit down inside the tent, while sitting on the OUTSIDE of the tent wall. Then, out of the rain, you can make your transition. Of course, there are other ways to accomplish this, but we at SD believe the awning/drop door/separate gear storage is the lightest and most elegant."
Yes, there are other ways. Like unzipping the vestibule and net doors, stepping into the tent, and rezipping the outer door after you. You have to stoop, but if you have to crawl, it is more of that poor tent design at work again. The one thing I do agree with is the value of awnings that can be locked down to create a closed vestibule in extreme weather, and opened up for ventilation in unblown rain and good weather. Hope we see much more development along those lines. Still, a zipper in the awning is needed for easy entry and exit sans the low crawl.
Will look in January to see what's up at SD when the new tents are posted. But as already noted by some others, lighter materials will be needed to attract light packers, and more functional designs as well.
Scott, please accept my apology for going off-thread.