Hi, and welcome to RC!
I'll put in my $0.02.
First, I disagree that a FOWLR is that different from a reef tank. It's true that you don't need as much lighting and current. However, it is important to keep water quality high. Most of the fish you are proposing to keep get quite large and create a lot of waste, so they will definitely need a decent filtration system. You can't skimp on water quality. Ammonia and nitrITE should be undetectable, and nitrATEs should be 20 ppm or less. I have found that many fish I keep are sensitive to nitrates, and show changes in appetite, coloration and behavior if nitrates get above 30 ppm.
Your stock list generally looks good, but I think you should definitely not keep the blue spotted ray, for a couple reasons.
Below is a quote from
www.wetwebmedia.com (which is a great site to do species research):
Taeniura lymna (Forsskal 1775), the Bluespotted Ribbontail Ray (3) (aka the Bluespotted Stingray in the pet-fish trade). Indo-West Pacific, including the Red Sea. To fourteen inches in width. A commonly offered species in the ornamental marine interest, but rarely lives... due to shipping trauma, being kept in too-small quarters, lack of oxygen, scratches and subsequent infections...
1) You didn't mention how long you have been keeping salt water, but this ray (and most rays) are really for advanced aquarists, IMO. They also have specific requirements that makes them not the best choice for a community tank.
2) Also, I understand tangs, angels and puffers (maybe even a little one) may pick at rays.
What species of lionfish? Valentini puffers are very small, and I wonder if it might not be eaten by the lion. BTW, a larger puffer might be a threat to the lionfish.
If you are going to keep a bannerfish, consider two, as they are one of the few butterflyfish that will school.
I wouldn't attempt the regal angel unless/until your tank is well established and stable. I'd also take a look at the regal angel thread.
I think with the fish load you are proposing, you are going to be way under-filtered. If you don't run a skimmer, you should have a good sized refugium filled with macroalgae, such as chaetomorpha, to export nutrients. Personally, I'd run a skimmer AND a refugium. If you are dead set against a sump, I'd run one or two of the best and highest capacity HOB skimmers available on the tank, and one or two HOB refugia as well (packed with macro and lit 24/7).
I have a barebottom 120 gallon tank that is pretty fully stocked (comparable to the stocking density in your list). A few years ago, my return pump for the sump failed. Since I had a 210 and was going to move the fish over, I didn't replace this pump. I put two HOB skimmers (one is an AquaC Remora Pro, one is a BakPak) and a HOB Aquafuge refugium on the tank. There is about 200 lbs of live rock in there too, AND I do weekly 5-10% water changes. While the tank is not ideal in how it looks, water quality is good. I've kept it healthy over the years and have not lost fish. It took me a lot longer to get my 210 set up than I thought, but I learned you could run a fairly heavily stocked 120 gallon tank with HOB equipment and a regular maintenance routine. If I had not had the additional filtration, though, I'm sure I could not have kept the tank going.
I would NOT put a DSB in the tank. Personally, I have been less than successful with them. If you use a DSB, make it a remote one that you can disconnect from the tank if it does not work out. IMO a macroalgae refugium is the best way to control nitrates and other nutrients. A skimmer can take junk out of the water before it becomes nitrates, and plenty of good quality live rock will handle the biological filtration - that's why I use all three on my more heavily stocked tanks.
I would also put more than 70 kg of live rock in the tank - more like 100 to 150.
If you want to run a skimmerless, fugeless, tank, then I think you need to seriously revisit your stock list. You will need to stock much less densely, and get smaller fish that produce less waste.
