I have had as a policy that every rule I add to the game, those that affect the players directly, must be something that takes virtually no time to play. For example, while my trading system is extensive, from my players point of view, it's just another equipment table (albeit one which the player's can't presume the prices from session to session--they have to look them up). My combat system is likewise. Although took me three hours to write out the details of two combat rounds, we would play those rounds out in a couple of minutes, with most of the time taken up in the players deciding what exactly they wanted to do. The system would not be the time-waster.
That's mostly the reason why I hated Rolemaster and the various systems that were birthed from those early attempts to add detail to the game. They were simply unplayable, as we sat around for hours waiting for the gamemaster to look up table after table. I remember one 24-hour session where we got into a combat involving dozens and dozens of troops against an attacking company of I don't remember what...and us sitting around and sitting around waiting for hit locations to be rolled and critical hits and Elvis in his sidecar knew what else. Killed that campaign.
Sometimes I struggle and struggle with a game idea that fails inevitably because it just takes too long to roll up the results. My efforts at treasure tables, for instance...where you want interesting, complex and bizarre treasure results, but it just gets tiresome at the end of a battle rolling and rolling and rolling out various pieces of jewelry, gems, furnishings, storeroom vittles, luxuries, armors, weapons, magic items, blah. Give me a system where I can produce an easily deliverable list in less than five minutes and I'm there.
I've been playing with the idea of just creating cards, possibly with pictures, or just blanks neatly cut by a print shop, which I can write up all at once, ready to shuffled and be dealt out at a session. Then the players can sift through the pile on the table and divide them up. The logic would be, it wouldn't be satisfactory for the player to write down the item any more...if he wanted to sell the item, or use the item, they better damn well have the card in their possession.
The hold up is that I'd have to create cards for everything they own now, and that's work I'm too lazy to do...but some session I'm going to get a complete list from them and go forward from there.
Another simplicity nightmare is weather. I've done enough interesting things with the weather in this campaign, since it started, to prove two things: A) parties fucking hate weather effects, no matter what they are; B) weather makes everything REAL.
About two years ago, the much weaker third-level party bought passage aboard a ship bound down the Volga river; the pirates aboard overcame them, jacked their possessions and threw them onto the bank--in November. The particular area, about 120 mi. north of Astrakhan, had a terrain much like the swamp from Lord of the Rings...ankle deep water. I worked for many hours prior to the session to produce believable weather tables, temperatures, rainfall, humidity, based off climate statistics from the area--and what followed was a very long session of absolute hell as the party staggered for mile after mile, trying to cross the great flat, ankle deep in freezing or near-freezing water, without proper gear or clothing. Without cantrips they would never have made it. As it was the half the party collapsed from pneumonia within a week and it was touch and go keeping them alive.
Did the party like it? No, they swore through the entire process. Was the adventure memorable? Damn straight. They remember it like they were there. They remember it because every day the weather changes marginally adjusted the nightmare, enough that they were praying for good weather--it really meant something to have it.
Although I've produced similar effects with adventures through deserts and, up until my hiatus (scheduled to end in two weeks, when I can run again, yay), through a snow forest, the actual creation of the weather is a superior bitch. As is the exact effects the weather has on the party depending primarily on what they are wearing and what climate they were raised in. So far, I haven't found an accurate, easy way to manage those variables and for the most part, they get ignored. That is, I unhappily treat the fur-coat wearing player far too similar to the player too stupid to buy himself a jacket, and is now wrapped with leather strips and deerskins.
But I feel I'm close to solving the problem. I hope I can sometime in the next few months, and maybe post the whole system here (that would be nice). At the moment, however, I'm stoked by the discovery of something called "clo"...which fits into an ad hoc point-value system I had earlier been using for clothing. Nice to find an accurate measure.