The same as me, my reluctance to use my Hunker is because, for me, it's too difficult to get in and out of. My primary concern is that if needed, how would I get out quickly and efficiently? An 'incident' I experienced in 2015 bought my concerns into sharp focus. At dawn 5 large white domesticated pigs tried to get in my tent with me! Getting out of my tent was easy enough, a quick zip of the inner and then the outer tent and I was able to stand up and fight them off. I've no idea how I would have managed if I had been using my Hunker at the time? Now that I've used both tent and bivi I now have a preference for bivi camping. My 'solution' for my Hunker, if it works, is for my wife's friend to slit open one side of it, 4' long and then sew in a 4' waterproof zip. My zip arrives on Monday so by the weekend I should know if it's a good idea or not. I'll let you know.
I also have a 3.5 Alpkit tarp (its very light and rolls up small) which I take with me as well and just erect it to cover my head and torso, once practised in the garden I soon got the hang of it. I use one of my hiking sticks to keep it at the right height and when it rains I just lower it nearer to my body. The tarp also has enough space to keeps my boots etc, in the dry. The very first time I used a bivi I took my Wild Country Zephyos One with me and that night I just erected half of the tent to cover my head. It worked but added together with my poles, tarp and bivi the package just weighed too much, which is why I bought my tarp. My ideal would be to find a very lightweight instant erection 'half a tent,' which springs into shape like an instant festival tent. I've looked for inspiration but have not found anything yet.
The other matter I found important was to use a large groundsheet, my bivi takes up half of it and in the morning and can stand on the other half to get dressed, sit and then sort my stuff out. This works very well for me.