A couple people are designing or have designed old school-style RPGs. I've made noises about planning to do one myself, although I'm not sure if I will concentrate on it before or after the atomic horror game I want to do; in either case, it will definitely be post-Liber Zero. At some point, I should give some detail about what I hope to accomplish and how it will be different. But I wanted to deal with one specific aspect of the rules that actually has some bearing on Liber Zero and old school dungeon crawl fantasy RPGs in general: space travel.
Rules for flying a space ship in a sci-fi RPG basically fall into two categories: space battle rules and long-distance travel. For the latter, I don't want a total hand-wave ("OK, 3 days later, you reach Proxima.") But on the other hand, I don't want it too complicated, and I don't want to make rolls for everything. And surprisingly, I can model how I want space travel to work by comparing it to how several dungeon exploration tasks work in the LBBs and their descendants. In particular, the task of opening doors.
We all know about "open doors on 1-2 on a d6" or similar open doors rolls. It's in the LBBs. But the LBBs also say (in the naval combat section) that 10 men can break down a door in one turn (probably intended to mean a melee turn -- a round, in other words.) Liber Zero changes this to 9 men in one round, using a technique that allows them to combine their action and strength, such as a battering ram; 3 men take 3 rounds.
There's no mention of making a d6 roll for ten men busting down a door. But then why the discrepancy? My assumption is that the die roll -- a Situation roll, in Liber Zero terminology -- is for those trying to "break the rules"; in other words, if you don't have ten men and don't want to take 10 rounds to smash down a door without rolling the dice, you can force it open in a single round with a Change Situation roll. Two men can force it open more easily (-1 difficulty,) and 3 men can be assumed to force it open automatically, but they must make an Avoid Accident roll or fall down as they break through.
So, the two rules are merged by assuming that you can trade speed for certainty. This can be generalized to many other tasks: spend 10 times as long to remove the need for a Change Situation roll, spend 3 times as long to remove the need for an Avoid Accident roll. Space travel, in this nebulous '50s rocket patrol RPG I want to do at some point, would work the same way: you can take the long, safe way to reach another planet, or you can cut the time down and roll for some kind of accident.
Of course, some things are always dangerous. There shouldn't be a way to avoid wandering monster rolls in a dungeon crawl (other than not adventuring.) And there shouldn't be a way to make a potentially fatal sci-fi task completely safe; using a superscience interstellar drive in an atmosphere or at low altitude will be a dangerous act, for example. You just aren't supposed to do that; you fly your rocket near the surface using mostly conventional techniques.
So, basically, Avoid Danger rolls can't be avoiding, Avoid Accident and Change Situation can be, by taking longer and using more people.