Wow, what a lucky guy to have room for a tank that size to play with! And with space for many clowns, I am very jealous!
You do realise I'm gonna bug you for regular pictures, don't you?
A group of 5-6 clowns in there sounds a good idea, like you've listed in your plans. 5 is probably best. I think with other inhabitants, and with a view to them living out a full life in your tank, that would be an ideal number. Any more and you might find they will 'over' dominate your tank slightly too. But! Y'know what you can do? You could add lots more loachfaces (as I like to call what IMHO are the best fishes of all!). Have you thought about other botias besides kubotai and macracanthus? There are many many wonderful species to choose from, such as modesta (similar 'max' size to macracanthus) and dario (6" on average, so a touch bigger than your kubotai).
I know your new tank isn't set up fully yet, but lots of extra caves and nooks and crannies for your loaches will go down really well with them! Kubotai, interestingly, much prefer bogwood in aquaria despite living in caves in the wild. Random fact for ya
Best of luck, and I am really interested to know how things go!