I don't know if I can add much. Never been to an Eco but have been to a lot of bashes.
Sometimes I get the impression that the powers that be want to make the National Bash as "rof" as possible. Now I don't mind roughing it. I've done plenty of that. But a national bash might be the wrong place to try and "prove" how tough we are. A bash is a party where friends meet and having good facilities and ablutions should not be seen as a sign of weakness.
Just talking in general here - I have not been to the last three National Bashes so I have no first hand experience of what the facilities were like.I do remember though that with the bash, I think it was in the free state somewhere, where there was basically nothing there, Piston Pete or LGF or someone summed it up nicely when they said: "I'm not going to ride a 1000km in a day to go shit in a hole."
The Eco could be reached as rof or as easily as the rider wanted? And no-one prescribed or cared?
Rough Rides should be rough and parties should be parties. If I want to do a rough tour I'll do that. The bash is about partying. If the venue happens to be at a place I want to tour that will work for me. That might happen in future. Especially if it's in the Lowveld. But for me touring is touring and bashing is partying.
The EC Bash and Breede Bash are events I will always frequent. Watty and Jupiter at the EC Bash took the organization to a whole new level. The venues are GREAT riding areas, the food is top notch and the facilities great. So you don't have to worry about the small stuff when you go, you can just go and party.
With Drinks on the Breede it's the same thing. No-one cares if you come with a self build bike via a 1000km twee-spoor or if you pop in with your car the evening of the party. It's not a toughness pissing contest it's a PARTY!!! And a very lekker one at that.

To me a bash is a bash is a bash. There is no distinction between them and one being called the "national" bash is not above the others. Anyone form anywhere in SA can attend any bash not so? The best ones will attract the numbers en flourish.
Lastly - Have a "national" bash in the Western Cape and see the numbers swell. Why? Because people go to events thats attractive to attend. Almost all WC WD's will be there (which is already more than your last number) and a fair amount of WD's from the rest of the country will also make a plan to attend. People from up country like to visit the Cape and do so regularly.
Have a "national" bash in the Transvaal somewhere and see how little WC WD's attend, very few? Capies don't holiday there.

Dislike that fact, criticize that fact, call it f-up. Cool. Won't change the fact though.

I certainly won't ride to the Transvaal for a bash with the established good-value alternatives I have around here at the moment.
Not sure this helps. It's merely ramblings and thinking out loud.

Dismiss the BS and take what you can use if any.