A little late to the debate.
There seems to be an assumption that selling your products here will be commercially viable. The products sold will be Marvelous patterns and hence only of use to other Marvelous users and software owners. There isn´t the user base of Daz or Poser for example.
I spent quite some time here on the forums picking up tips as well as trying to help fellow users and my opinion is that the vast majority of users here are making their own clothing. Indeed this is the biggest draw for most. With the current collection of freestuff in the marketplace there are enough basic garments to take and use as a base to build your own designs.
Most 3D artists would not wish to use an existing pre-made garment when it is relatively easy to make your own. Copyright could be a problem too. Garments have a built-in watermark; the original creator, so in a commercial sense I´m not sure if you purchased a product you could change it to any great extent. You couldn´t use it as a base to make your own garments and then sell, for example. This is another argument that limits the appeal of the marketplace to most users.
I am an animator and it is my understanding that it is perfectly acceptable for me to make MD clothes to use in my animations that are sold to clients. This is using just the personal license. BTW ZBrush, as stated, is hardly a comparable option for clothing animation.
In summary, I feel the delay of an active marketplace is not a significant drawback. You are certainly not losing any substantial revenue by it´s unavailability.