Hey man, I just picked up my Hiatus last week and am currently chilling in it, on the Oregon coast.
The bed foam is decent for only being 2" thick. I wouldn't say I got the best sleep, but it's not rock hard like the GFC foam. ? I'm currently trying out an Exped Megamat Duo 15 tonight. It doesn't quite fit perfectly, as it's a tiny bit too wide and long, but I made it fit width wise (it's only about an inch oversized, but it's inflatable.). The end just hangs a couple inches off. This takes a bit of time to setup and tear down, but it could solve your bed comfort and closing issues. This 15 (6") is massive, so I'll probably downsize to the 10 (4").
While it is not recommended to close the top with the bed deployed, I tried it and it will work. BUT, the interior handles will press all the way into the cushions though, so that pressure will eventually warp the side panels and/or dent your cushions. If you replaced the hard plastic handles with something like 1" webbing/lashing strap, you could negate that issue. You really only need the handles to close it, and even that "can" be done without them. I also don't push the platform all the way in to close the top, only enough to clear the handles, which is like 8" on mine. I put the three cushions down low and leave my bedding up top. Easier to manage three cushions vs wrangling two blankets and a pillow. ??♂️ I could probably get away with leaving one or possibly two cushions up top with the bedding, but I haven't bothered.
With the Exped, I should be able to just open the deflate valve and let the roof squeeze/deflate it. I would leave some air in there to help support the panels when closed. I'll test that theory tomorrow.
BTW, I always experiment with things outside of recommendations, so this is not an invite to do what I do. Only that I have tried something that was "not" recommended.
Pic for fun, from a few hours ago.
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