The point of the rule is to make all nations able to compete on land and sea. I believe the reason moves are allowed between sessions is because it was considered too hard/troublesome to police midsession and considered too high a cost to move.
I'm not sure what you mean by "allowed between sessions," but the rule seems to be meant to permit midsession slider moves to allow players the tactical choice to make short-term changes to the quality of their military if they deem it useful, without disrupting any long-term equilibrium.
So it seems to me what you're describing as a problem is actually what the rule's supposed to do. Also, looking at the stats and events, it doesn't seem like anyone's actually moving sliders. I know I haven't, and with the exception of HAL's +3 Land (which was caused by an event), no one has touched it in at least 4 sessions, and I'm willing to bet every slider move before that was event-based too.
Now, the slider should be reset between sessions, but that's Drake's fault and has nothing to do with the rules.
Rather than try to figure out how long people were at +3 we just assume they were at it half the time.
FAA rules as I understand them (to be confirmed by drake)
You get an extra leader of your choice for your first FAA and one more for every three after that. So if you have no other leader bonuses (quantity, decentralized etc) and one FAA you'd get five leaders. 4 FAAs and you'd get six leaders. The stability bonus is 30D per luxury manufactory per year of the session. Rather than try to figure out how long people were at +3 we just assume they were at it half the time. I'll post the FAA stability edits to save drake the effort, I guess it's up to each individual to claim their leader bonuses.
Sorry, I didn't see this post before. Stab will be edited in between each session. You get 30D per manufactory per year, what your stab was during the session is too hard to track and so is ignored for this rule. Example: If you had 1 luxury manufactory last session you'll get 30D x 26 years x 1 luxury manufactory = 780D edited into your stab investment.What does this part mean? Will stab be added in-between sessions, and what relevance does +3 stab have?
And does "extra leader of your choice" include explorers and conqs?