I suspect this would be a tricky one to add to the system but maybe a worthwhile one to look into. add a frequency score or count to the system based on number of times the system inports a particular word. this would be useful in adding a tertiary selection criteria for frequency weighting during SRS review selection. primary should be familiarity rank, secondary is time since last progression.
That’s kind of already a feature, if I’m understanding you correctly. Each LingQ has a number of coins associated with it, which can be seen to the left of the tags and below the TTS play audio button. The higher the frequency/importance of that word within the language, the higher the number of coins associated with it. On the vocabulary page, one of the filter options is to sort by “Importance”, which puts higher value words at the top of the list.
As @rhess wrote, that feature already exist but not in all languages at the moment. However in languages you are learning (German and Japanese) you can sort words by importance.