The commercial theme repository was (I assume) created as the WordPress theme industry was deemed to be unacceptably biased towards non-GPL themes. However this does not seem to be the case with plugins. I don't know of any popular non-GPL plugins but until recently I could rattle off the names of a whole stack of non-GPL themes, most of which were far better than their GPL counterparts.

So no, I don't see much point in a commercial GPL plugin repository.

I already have plugins with commercial features in the repository. Since they're 100% GPL they're already in the repository. Moving them to commercial repository may give them more exposure, but I can't see that benefiting anyone but myself. A decision to create a commercial plugin repository should be based on how it benefits the community, not how it benefits greedy plugin developers. If encouraging plugin developers to create better plugins by allowing them to monetize them whilst still having them promoted by WordPress leads to improved plugins across the board, then sure, a commercial GPL plugin repository may make sense, but I doubt it would.