I think I can get behind the modifier idea. In that sense it’s a little more like a traditional stat since an emotional character is not necessarily ruled by emotion but knows how to channel it, and it’s reasonable (especially in the limited context of a game) that it would be harder to remain detached at the same time. Although I would still contend that in that case it might be better to have two normal stats (maybe ‘Heat of the Game’ and ‘Keeping Cool’ for thematic appropriateness in a tennis setting) that can both be trained if someone wants a character who can be detached when necessary but also get the maximum for exerting themselves. I do think that in real life the best athletes (and more broadly the best at many things) are capable of both. Of course, training both might come at the opportunity cost of increasing other stats.
The modifier idea is also closest to what I was talking about in Tower Behind the Moon. In that case, I think it helped that the character was painted as exceedingly powerful and also that the writing gave me the sense almost that I really was reading or creating a second-hand legend about a great wizard, so it made sense that some traits were emphasized in recounting over others that the character possessed in similar abundance but less prominently (for example, a Quick to Anger wizard could be as clever as a Subtle one at times, or one who preferred Dynamic magic still obviously having a solid grounding in Ceremonial casting. Even a mage who was Light as opposed to Heavy remained evidently more physically powerful than a nonmagical human). As to whether that approach would work in a tennis game, I can’t really say.
I’m not so sure about the opportunities and perception ideas. In general, I think opportunities in choice games are better off being controlled by what the player does, or a stat that represents what they can do. Otherwise it takes away from player agency a bit: ‘Sorry, you’ve been too emotional up until this point, you can’t now be unconcerned about this’. I have seen that in games before and didn’t enjoy it. Unless of course it’s already being treated as more of a modifier as stated above, but that’s slightly different.
Similarly, when it comes to perception, I’m not sure it works well when governing how all characters respond to the MC. What if they are by-the-book when interacting with their professors but know they can get away with a lot more in front of Mother? I think it’s better to base that off of how the MC’s individual encounters with each character went. Maybe it might work as a general kind of ‘reputation’ thing, but even then reputations are generally not so black and white. Two people can have completely different opinions on a particular action.
As an aside, I do agree that chaotic/lawful could actually work, out of all the proposed pairs and perhaps any possible pairs, but for the reasons given above I’m not sure it should govern any game mechanics, and if it didn’t then it would really be nothing more than a less-accurate-than-if-strictly-numerical tally of chaotic vs. lawful actions.
Opposed stats fit very well with the human urge to classify–not to mention that seeing blue and red fight for control of that bar is probably as visually compelling as it gets in a game devoid of images. Even so, at their best I think they still fall short of what well-executed ‘normal’ stats can do.
I can’t really comment on Jungian theory, not really knowing anything about it, but it sounds interesting from what you describe. Maybe I will go find out more.