Honestly, I don't see the need for this kind of a rule. A lot of things could happen. Here are just a few examples.
I believe the intent of this rule is ensure SGTOM doesn't become a competition where on some teams, a single player or a pair of players play the vast majority of all turns of a game. It is a succession game after all and not an individual or pairs game.
There is a problem to address when a single player plays over half of all the turns in a SGOTM. There is a similar problem when two players combined play over two thirds of the turns in a SGTOM. Frankly, in both cases its hard to think of it as really a team effort at all.
Some players might be busy for the first part of the game (can comment but not play turnsets) and will commit to playing later turnsets but then the team could unexpectedly win 100 years earlier. I, myself, am terrible at predicting ending dates, and while a few players can do it reliably, the emphasis here is on the word "few." It's a very plausible scenario.
In my opinion, the rule simply needs to be enforced only at the end of the game. The team must adjust their players' turn totals to comply by the end of the game or it will be disqualified.
Some players could be incredibly active in terms of discussions, making spreadsheets, digging-up info, or even just providing a strong guiding hand of experience. These players may have little or no turnsets in the game yet their contribution could be huge. How would you objectively judge this level of participation? I claim that you can't, at least not in a feasible enough manner to warrant doing it for this kind of game. Who is to say that "playing turnets" is more dominating that "telling other players what to do"? I would actually tend to think that the latter can have a huge impact on the game, yet I don't see mention of putting a rule on commenting about other players' turnsets.
The concern is over who actually plays the turns. Lurkers are ignored with respect to this new rule, because by definition they play no turn sets at all. Team discussion is also irrelevant to the reason why this rule should exist as well. This rule must prevent the extreme of "one person literally playing the whole game himself". We should all be able to agree that if a SGOTM team literally had a single player play all turns of the game, that game should be ineligible for any awards. This rule is intended prevent something close to this from happening, where a single player or two players combined are playing the vast majority of all turns in the game.
What happens if real life gets in the way and some players have to drop out or don't have time to play turnsets? Are we going to say "oh, we're terribly sorry, but you lost the game, because all of your remaining players have played too many turnsets/too high a percentage of the game"? It would be quite unfair to everyone on that team and would put a lot of unnecessary pressure on people who had unexpected real-life events get in the way, since not only would they have to deal with terrible real life issues, but they'd have to deal with the guilt of having disqualified their team!
When a Team doesn't meet a requirement of the SGOTM win, their entry is disqualified (can't win laurels). If a team failed to properly plan their turn set and can not comply with this rule, they should resign. We can't guaranteed that all SGOTM teams that start a game will complete it. Some teams abandon games for the reason (real life) you state above.
Yes, it can get silly if more than half of the team ends up lurking, but trust the players to resolve this kind of an issue ourselves. Taking OSS as an example: we had half of the team lurking or no-showing last game. Those same players are not joining again. We, as a team, have resolved the issue. I trust that other teams will be able to do the same kind of internal team management far better than any set of conditions on playing time can accomplish.
If only half a team of six is actually playing, it is still quite easy to comply with the rule. Just split the remaining turns among three players, and no one player should end up with more than 33% of the total turns.
If only two active players remain, it may be difficult to comply with the rule. That should be ok, because a team with only two active (non-lurking) players should probably resign, unless they are very close to completing the game in two "normal" sized turn sets. A 60t turn set would not pass muster in this regard.
When a team loses literally half their active players, perhaps they should resign rather than complete the game with just three players (their choice). If a team is down to only two non-lurking players, its not really much of a succession game any more and should probably resign.
Maximum Turn Set Length:
Going back to what
AlanH said about a maximum turn set length: This wouldn't actually solve the problem entirely. Two players could hand off to each other, other players giving real life excuses not to play and comply with the maximum turn rule easily, yet they would play all turns of the game between them. However, it may the simplest way the solve the problem. Teams often start the game with a very long turn set, so we may want to defer enforcement of this particular rule till turn 50 or turn 100. I'm fine without this deferment too. A maximum of 25 turns per turn set seems reasonable.
Can someone else, please comment on these two proposed rules?
Sun Tzu Wu
