The way I think of classifying the grade of a clause is based on the three dualities of Pre-Battle & Battle, Unable to Proceed & Select and What Will & What Could Happen. Grade 1Ai - One cannot proceed with the something that is disallowed. Grade 1Aii - One cannot proceed with the something that could be disallowed. Grade 1Bi - One cannot select something in battle that is disallowed. Grade 1Bii - One cannot select something in battle that could be disallowed. Grade 2Ai - One cannot proceed into a battle with something that is disallowed. Grade 2Aii - One cannot proceed into a battle with something that could be disallowed. Grade 2Bi - One cannot prior to a battle, select something that is disallowed. Grade 2Bii - One cannot prior to a battle, select something that could be disallowed. It's interesting that Sleep Clause, Freeze Clause, Evasion Clause and OHKO Clause in PO are grade 1Aii according to my system. But something like Species Clause is effectively 1B. I guess my foundation of what could and what will happen is a bit shaky because it depends if it's on a turn by turn basis or a potential basis in a future turn. I'm finding this quite tricky to classify and have changed my mind several times. I'm wondering if someone has a clearer way of thinking about this.
hmm.. interesting. Have not thought about clauses much in this way, but the known clauses pretty much fit into these: What you can bring into battle. -No Ubers/other tiers for non-OU metagames. -Species Clause. -Soul Dew/Berry Juice Clauses. -Item Clause. -VGC/LC Level Limits. -No OHKO moves may be on your team. -No Evasion Boosting moves may be on your team. There is also an assumed class of these which disallows anything which can't be obtained legally in game, such as illegal movesets and above level 100 Pokemon. What you can do in battle. -No sending two opposing Pokemon to sleep (Sleep Clause). -No Freezing multiple Pokemon. -No Evasion Boosting moves may be used. -No OHKO moves may be used. -No spending more than <time> per move, with a starting extra time of <time>. Clauses can also be "soft", "hard", or "game bending" depending on implementation. Soft Clauses can be broken, but you automatically lose the match if you break them. They should come up with a popup warning on any sim. Hard Clauses directly prevent you from breaking them (moves can't be selected if they have a chance to break the sleep clause, Evasion/OHKO moves can't be selected if their respective clauses are enabled). Game Bending clauses alter game mechanics in order to avoid them being broken, like sleep moves failing after first use or Ice Beam never freezing after the first freeze. This is somewhat similar to your system, but I think the distinction between "Will Happen" and "Could Happen" is not needed, because there are so very few situations where something will certainly happen that "Could Happen" clauses are the only useful ones. And I have included an extra class of Proceed/Select since many sims use incorrect mechanics to more easily implement tricky clauses. Another thing to consider is exceptions to the clauses, for example a trapped Pokemon encored into Spore. You obviously can't do anything but use hypnosis, so if your opponent switches after you sleep their first you will lose despite having no choice to do anything else. This creates an alternate win condition. You don't have to aim to KO your opponent's Pokemon, just force them to break a clause. So, most "Soft" or "Hard" clauses should have exceptions which allow them to be broken only when there is no other possible choice. Personally, I think pre battle clauses should replace in battle clauses as much as possible. They are simple and unarguable, and impossible to exploit for both players. The Sleep and time clauses are the only remotely sensible ones without a pre battle form.