I think Memrise could benefit from offering a “comprehensive review” feature that will test knowledge of a complete deck or a certain threshold thereto. The first option occurs in fact, albeit sporadically, with Speed Review in the most comprehensive case. The second option could add an extra concept to existing proficiency, which would be of greatest benefit to decks that teach basics first, such as articles & transitional adverbs & number systems common and formation of words from symbol. Many Latin and Asian decks currently employ this presentation in decks, and other decks present piecemeal options to hit each area of focus apart.
If you can imagine that a comprehensive Hanzi/Kanji Chinese deck hits upon radicals and graphemes that comprise logograms from primitive, single-characters to complex mish-mashes of multiple graphemes all in a single character, you have in essence an ideal solution IFF you can decide to cover or test yourself on comprehensive proficiency based on the precise number of graphemes inolved. Of course, your deck designer would have to have some way to designate when a set of words belongs to a new proficiency level, but that should be simple to program or work with next to a system where you can add each word with a checkmark if you want it to belong.
Really, the lightening emoji offer perfect basis for a comprehensive test based upon ongoing critical interactive dialectic. But Memrise has a whole new set of ways newly unexplored to develop a more AI -orchestrated potential on such grounds.
Just my 2¢ for the best reason to keep turning to Memrise.