Plant was from a overrepresented franchise. Of course plant is a well known obstacle, there was imo no need for it to represent the Mario franchise, as it was pretty well represented.
If we are to get any generic enemies at all I'd be for enemies from less good represented franchises. So no goombas, no zubats, no koopas etc.
I'd prefer something like a Kremlin, a bokoblin, heck maybe even a Deku plant as a plant echoe, I know bandana dee is his own character, but since he is a waddle dee he is kind of this middle ground as the one outstanding character among the generic enemies...
I have to say the longer I think about the less excitement I find about this idea. Those slots could be given to much better characters than generic enemies. A Revali would serve much more purpose to the roster than a bokoblin, dixie or cranky would do a much better job in representing the dk franchise than a kremlin, Isaac is from the biggest currently unrepresented first party franchise and should actually take priority over a generic enemy type, It might be an unpopular oppinion but waluigi would represent the Mario franchise better than for example a Goomba, a Koopa or a Piranha Plant. The same goes for Geno.