Hey Kevin. I've kept patches of val in Malawi tanks many times, with hit and miss results, as Pitbull and efors have already said. I'm a stickler for maintaining realistic biotopes, to the extent that I won't put S. multipunctatus in with Malawi fish. So except for a lone pleco in my first Malawi tank, I've never kept any fish with my ACs on an extended basis except Synodontis multipunctatus (with Tanganyikans), S. njassae and Chiloglanis neumanni (both with Malawis). The last two took several years and small fortunes to acquire here in Wyoming during the mid-1990s. S. multipunctatus maxes out about 6", with 4.5" to 5" being average. Think efors may be thinking of S. granulosus when thinking of a Tanganyikan syno getting to 12". S. njassae maxes out about 7" (5-6" average), but used to be a bear to come across. C. neumanni is a small (3.5" max) sucker-mouthed algivore, also hard to come by at the time.
I've used giant danios as dithers on numerous occasions in breeding set-ups. I'm not a loach person anyways, but I do know a large number of people who have successfully kept clown loaches with ACs long term.
If this was my tank, I'd skip the loaches, the RTBS, and the BNs, acquire Malawi synos, and plant the val. But this isn't my tank. It's your tank. A case can be made for either including or not including every fish you've listed in this thread. I don't think anybody has an issue with your stocking density, now its your choice as to which synos, suckers and/or loaches you choose to add, with the information you have on the pros and cons of each species. Whatever ya do have fun with it!
WYite