That tank would be good from a sanitation aspect. It's way to over-crowded from a health stand point, rule of thumb is 20gl 1st fancy gold fish the
+10gl for additional. So maybe 3 baseball sized fancys in a 40-55 gl tank.
I don't care for the "Train Station" look of too many fish in a tanks (especially bigger fish) pacing back & forth.
I like your thoughts on a few simple plants. I thought about a weather loach but they really like to burring themselves in fine sand And I don't want to have any substrate in mine. All planting will be in clay pots. Weather loaches really should be in man pairs or trios tone happy. The also get to 9-10". I do like that they are cool water fish like fancy goldfish.
I would advise to take one's time and find the nicest specimens. You can find info on several fancy gold fish sites. Since they can live well over 10 years it worth the effort to pick a young fish that will have resale/rehome value. Look for thing like uniform fins, correct lenght to body, body shape, clean colors and markings etc.
Here's a good page on what a proper Oranda should look like:
I've occasionally seen very nice Orandas in PetSmart. It's rare but they do show up. They bodes are usual fine it's the fins that you need to examine.
I was thing the same as you on my cycles 15 on - 45 off during the Photo Period.