There was a concept common on the convention circuit a few years back...actually, now that I think about it, it was a few decades back.
Like many concepts, it didn't have a name when it was in vogue, and it was only when people stood back to analyse it that it was categorised with a title. It was generally called a "pieces of paper freeform", "paper-chase LARP", or some combination thereof.
A true "Australian Freeform" (a misnomer because it's a vague concept that I've discussed previously (here, [pt2], [pt3], [pt4], here and here) has no rules. Well it has the social rules of human interaction, the rules of etiquette appropriate to maintaining genre convention, and the rules of an imposed space of shared imaginary narrative facilitated and guided by the GMs...but it typically has no written rules. Instead, this style of game may have elaborate character kits with a page describing the setting (everyone gets one of these), a page describing the factions in the setting and their generally accepted relations to one another (everyone gets on of these), a page describing specific members within a faction and how they relate to one another (everyone gets one of these that has details the faction their character belongs to...there might also be factional goals on this page), a page describing specific thoughts on other characters (everyone gets their own specific one of these, often providing thoughts on the main characters of the event, the other characters of their faction, and a few assorted links to other characters in other factions who they might have a history with), then finally each player is given a set of goals that typically require the help of other characters before they may be accomplished. That's about five pages per character, with two pages being generic, one being faction specific, and two being personal. In a 20 player game with 4 factions, that's (1+1+4+20+20) 46 pages that the game designer has to write up.
...and that just covers the social interactions of the session.
The last thing you want is a complicated system on top of that.
A "paper chasing freeform" has loose mechanisms, typically working with the idea of set collecting. Every player might start with two or three different types of card and every player is similarly given a goal of collecting a specific set of cards. The types of cards and the types of missions vary depending on the scenario of the game. It might be parts that can be combined in a sci-fi setting into technologies necessary to progress to the next stage of the game, it might be components for an artefact, assorted bits of information to be combined into an ancient prophecy. Once the pieces have been collected and cashed in with a GM, new cards might be distributed, thus allowing the sets of other players to be completed (other players might find that their goals are no longer possible because the cards they need have been cashed in with other sets).
At the start of a game like this, everyone tends to be wary of one another, especially if cards for a set are scattered across multiple factions, or between known rivals. It usually takes half an hour or so before the first collections of cards to get cashed in, and typically these first collections come from groups who were already working together, or characters being played by people who are friends out of game. Once the first card collections are gathered, and the effects of this are felt on the wider narrative of the game, the impetus to complete collections gets ramped up among the other players. It's a nice system that imposes a natural escalating pace where the only real rules are still very intuitive. Unfortunately, for a while at conventions it was over used.
A few other simple mechanisms like this can be added into a game without requiring players to "learn rules". I like to use them in an irregular rotation, giving each game a slightly different feel. In each case using them as cap-systems separate from the core mechanics of play, whether those core systems are the loose minimalism of "Australian Freeform", or a more structured set of formal rules. The thing I usually find is that it's these cap-systems which often provide the most flavour and interest during a game, and often the best anecdotes and war stories once it's over.