I was just thinking about having a counter (need_sleep),
just example but let's say each hour of sleep substracts from it 10 points, each hour of not sleeping adds to it 1 point or 2 points during night hours (unless player is "night creature" - perk possibility, which will add 1 point during night hours instead of 2).
Every 10 points player gets minus points to SPECIAL and/or skills. When it reaches 0 (in case of SPECIAL, therefore possible no-sleeping length would be 100h)
player dies from being exhausted from not sleeping.
During travelling on the map, every 10h player would stop with message "Your are sleepy, want to take a nap here or continue travel", YES/NO.
Yes opens map with no(?) enemies where you can sleep, during sleeping on the world map there would be small chance to be approached by creatures (enemies/friends/npc/animals), let's say PERCEPTION would influent how early you wake up (very low = you wake up when they attack you, very high = you wake up when enemy enters map)
uff.... just had this idea, might seems compilcated but it is just base on 1 integer value (+possbile perk?) and pentaly system could be base on same as chem addiction
what you think anyone ?