@Lady @aescling i think it varies depending on the specific challenge.
tho to answer cat's question, this idea seems like its big advantages are that it would encourage one to use mons you otherwise might not by randomly shrinking the available pool of mons (as is common in e.g. nuzlockes) but without bias against infrequently-appearing mons
re: idea for a pokémon challenge run
@Lady @aescling wait are you doing this in your current HG playthru?