For F2P users this wouldn't matter, but for SpA forum members I have an idea: what if we had a system that would give more spapoints to classes that are less used and less spapoints to classes that are more in use?
For example if there's 4 demomen in the server/team, being a demoman would give you less points per minute. If there's only one medic, being a medic would give more points than being a demoman.
Say you get 1 spapoint per 10 minute playing in the server by default.
If you play a class that's in use by more than 3 other team members, you get the default amount of points.
If you play a class that's used by 2 other people in your team you get 2 points per 10 minutes.
If your class is shared by 1 other team members, you get 3 points.
And if you're the sole representative of your class in team, you get 4 points per 10 minutes.
Or whatever the amount of points, that would make sense if there's usually 2 users of every class in a team.
And maybe even distinguish the points by 3 groups: attack, defend and support classes. So if there are many support classes and only one attack class, it would add another point to the attack one?
I know this sounds pretty complex, but in theory this would be exactly what Saint mentioned: stimulating, not of limiting. But yea, in practice, personally I don't think anybody cares about spapoints that much.
Also, since my idea is quite crazy for a custom plugin, I have to go with yes for class limit: 4.