As for the non-English speakers finding the collective difficult; I can see that. I have not specifically considered their needs whilst compiling the guide. In the case of `flora` I am guessing you're thinking `plant`?
Speaking from experience, you can't even expect native speakers to know all the collective forms. Worse, in some cases the collective form may cause confusion if the collective is the singular of a different table (players in a team, teams in a league, doing a fantasy football league app).
Using the plural, your schema would be player -> team -> league. Using your system, it would be team -> league -> sport. Good luck explaining that to a new hire.
Not all players will be on the same team, but they still participate in the league so I disagree with this example terminology shift.
You would end up with a slightly more generalised naming like this in my opinion:
- athletes - teams - leagues
In this particular case there are no suitable collective terms.