I wouldn't get stuck on NLS being the be all end all of fish food... with any marine fish including angels I think a variety of food is good. I fed my fish including my regal NLS, mysis, cyclopeeze, noori and a frozen angel formula and my regal still got HLLE. So who knows. Probably a good bet to have a good amount of established live rock around for grazing, and probably a good idea to keep some rock in the sump and switch it out into the display for some variety on a constant basis.
I used a frozen food from Aaron at Big Al's, all my fish liked it not just my angels (has sponge). I think it was called Angel Diet. PM him and he'll let you know. There also is Angelixr which is a liquid additive for other foods that is supposed to be the same in terms of make-up as sponge. I read that it isn't sponge, it is simply a mix of proteins, AA's, etc. that is the same or similar to what is found in sponge. Couldn't hurt though.
I can't see why you couldn't keep Moorish Idols, I've looked into it myself. They are definitely not a beginner fish but if you go on RC there are plenty of people who have had success. They do need a lot of attention and care by the sounds of it. I'll be interested to see how you make out
