I'm also not clear how the rules would work on this. Say you had two classes
Class A and Class B and initially both had equal votes. Art 3.2 refers to "directly or indirectly" altering the rights of a class. If you had a resolution that said all Class B members had 1000 votes each, you could say that the rights of Class A members had been indirectly varied. Art 3.3 says rights can only be varied by a resolution of the class - would that cover indirect variations like this? My experience of similar clauses in the commercial context is that it probably would - although those are normally much more clearly worded.
That's certainly a plausible explanation, I've no idea if it's the right one!
Remember, giving powers to the directors doesn't mean the membership can't do anything about it - a general meeting can pass an ordinary resolution creating a rule (under article 28.4) saying the board has to put everyone in the "general members" class (or whatever you call it) unless they have the permission of that member. (I assume the board can't change a rule added by a general meeting, although that isn't explicit... it's probably in the Companies Act somewhere.)
You could read it that the Board could create a rule that said "A", the general meeting could revise it to "B" and then the Board the next week could change it back to "A". As you said this would be crazy, but there is nothing in the Articles that explicitly says they couldn't. I can't think of anything in the Companies Act that would prevent it either.
I can't find anything in the Act that's relevant.
On the other hand, the members could pass a Special Resolution which restricted# the powers of the Directors (under Art 15.1) but this would need 75% majority. The directors wouldn't be able to over-ride this.
That shouldn't be necessary, though...