Memory Traits

[kamiluzbx]

Having a memory system slowly picking away at certain skills would be pretty interesting.
like having 3 or 5 levels of memory, like normal memory would be maybe 50 exp loss every day starting after 3 days of not doing that thing

schizophrenic randomly forget certain skills for a certain amount of time and other symptoms

maybe something in between because schizophrenia is a bit extreme

forgetful 125% exp loss

average memory (no trait)  100% exp loss 
good memory 75% exp loss

hyperthymesia 25% exp loss

the traits should be very costly to make them not god-tier just something you have to live with

[Axiomatic]

As an idea/ game mechanic, this is very interesting since it gives skill acquisition and growth an impermanence and vulnerability that creates real risk/reward decisions for the player, similar to how having permadeath makes the gameplay that much more riveting with the choices you make. It also simulates real life to a degree. The tough part is really working out the values that drive the loss/retention of memory so that it isn't too overwhelming and greatly hampers the fun of playing.

 

Having a grace period before the memory/skill loss occurs is definitely a must. One of the fundamental questions to answer is can it actually make a player lose a skill level or does it stop once it depletes the current level? And how much skill memory do you lose a day after that grace period? Also, much like the old adage about riding a bike, gaining back that lost memory should happen much faster than when first acquiring the skill. Either through doing the activity or rereading a skill book of the level the character is at. For instance if you're halfway through lvl 7 carpentry, and then lose all the skill memory down to the start of lvl 7, once you start doing the activity again you gain back XP at 2 or 3x the original learning (including skill book multiplier) until you reach that same halfway point, where skill learning then goes back to normal levels (modified by skill book multiplier). Or perhaps as a way to make the memory loss something to manage but not overly time consuming, allow rereading a skill book of the appropriate level to fully return your skill to where it previously was, in this case halfway through lvl 7.

 

Sleep deprivation could also accelerate memory loss as it does in real life. 

[kamiluzbx]

Going off of what you said, "One of the fundamental questions to answer is can it actually make a player lose a skill level or does it stop once it depletes the current level?" maybe a system where the skill lost from memory is greyed out and when you gain back that skill your character gains random bits of skill back whenever you perform an action. Or it just is regained at a 150% rate as opposed to gaining new exp.

But if you don't go back and try to regain the skill after the current level is depleted for another grace period of say, another 3 days, it depletes at 90% of the initial skill loss.

Books would "reinforce" the exp meaning the grace period is increased or the exp loss is stalled for another few days, and exp gain (like usual) is gained at a increased rate.
The book can be reread and everytime it is reread then the reinforcement bonus would be increased by maybe 5% every reread and exp gained would increase by a percentage as well.

Sleep deprivation would make sense to accelerate memory loss as the game mirrors real life as best as it can without going too far.