it could be better planned but what would be your reasoning in making the AE/marketplace completely separate? not sure i see the sense in doing that.
having a page dedicated for selecting what you want in your client i think is a good idea.. something like the app store on android but it would have to be easily accessible and easy to find
For example, a conservative user who wants to use NXT only as a standard currency, perhaps doesnt' want to see all the drugs & porn offered in the Marketplace
But disregarding this, I think the main client should do only the basic functions of a cryptocurrency client and do them well (e.g. Unix philosophy). The bloated standard Java client consumes a LOT of memory actually, much more than the clients of the Bitcoin family. I don't say AE/Marketplace should be completely separate, but as Marketplace and AE actions are ordinary coin transfers or messaging, I don't see why in the standard client there should be a gui for it. Ideally the Marketplace/AE should be plugins.
the marketplace doesnt show the items for sale.. you gota find the itemID and search for it.. the marketplace could only sell drugs and porn and lots of it but that wouldnt matter because users would not know the ID and therefore would not see it. i dont like the way the marketplace is or the fact that nothing shows unless you know what your looking for.. but it was the best of a bad situation..
i havnt checked memory usage of the client but its never affected the running of my computer in any way so i dont see that as an issue tbh. plugins would be good too..