So if I understand you correctly, you need a bivy because you are going back to a tarp. Correct?
I am a tarp guy, and have been one for 40+ plus years. If there is a combination or style I have probably tried it.
Until a couple years ago, my lightest and most common set up was a poncho/tarp with a bivy. Bivy only required because a poncho/tarp does not provide as much coverage as a larger tarp. For a year I used a MLD SilNylon Poncho Pro and a MLD Soul Bivy Side Zip almost exclusively. I cannot say enough good things about the system, especially the side zip bivy. The one thing I hated about the bivy was the bug net. I just don't like nets in a bivy. I would have just cut it out, put didn't in case I ever wanted to sell it. Bugs are rarely a problem where I hike because they don't like me and I don't like them, but sometimes I use a head net. At night the bugs go to sleep when I do.
I really prefer a large tarp (8 X 10). But the poncho/tarp & bivy was the lightest set up at the time. Then came Cuben. So for over a year I switched to a BPL Nano Tarp and a Marmot Essence jacket. Less weight and more coverage when sleeping. No bivy needed. I was much happier.
Then a few months ago I saw the zPacks Hexamid and the poncho/ground sheet... now we are talking less than 7 oz for shelter, rain gear, and ground sheet if you use trekking poles.
I have a Wild Oasis (same set up as the Gatewood), and like you always knock condensation down on me or rub against the side. It just never worked out. And I had visions of similar problems with the Hexamid. Never happened; there is plenty of room in this small shelter and I have had zero problems. You can buy a separate CF pole at 1.1 oz for the Hexamid, if you don't use poles. I have stopped using trekking poles and find the CF pole a little flimsy, so I am looking into an alternative.
Now, how do I like the zPacks system? Absolutely in love with it. Quick set up. The ground sheet clips to the shelter with optional clips and becomes a bathtub floor, which makes it easier to organize things, and is much, much bigger than my polycro sheet. Normally in good weather I skip a shelter. But I like this shelter so much, I have set it up on every trip since I got it, which is something like 6 or 8 trips. In poncho mode, it is the best poncho I have ever used, because it is not as big as anything I have used in the past. It covers my UL pack, the hood works fairly well, and it goes almost down to my knees (I am 5' 11"). Although not sure it will be large enough to cover my McHale LBP 36. Yes I am a little concerned about using Cuben as a ground sheet and rain gear, but so far, so good. I got the Lite 1.0 cuben poncho. Some people worry about spray coming in the open side of the shelter. It does have a little bit of an over hang, and I haven't had any problems in the rain to this point. Joe did the CDT with this shelter without a problem, and some of the time his wife joined him in it. You can get an optional beak.
So... no bivy needed :)
P.S. In snow I use a tent.