Defenders of the New Century has been primarily designed around campaign play, with the intention that a player will play a single character across around 20 sessions of gameplay, slowly improving as time goes on and experiencing their own narrative arcs as they go forward. There are some game systems which are developed purely with this in mind, namely the Luck point system, and the Research task system.
We run into 2 competing needs in any tabletop game that involves combat in any way. We want, or perhaps even need, death to be a possible consequence in gameplay as both an excellent motivator against failure, and as a way to keep the tension high throughout an encounter. It also helps that death is a predictable consequence in combat, which is good for the internal consistency of the game.
The problem with this is that we really, really, don’t want to actually have to kill characters when it comes down to it. Players fundamentally care about their characters, and we want a character to exist for an entire character arc to get the most joy out of said character. To maintain tension and make sure that combat actually feels dangerous, we want to have situations that gets characters close to death, without actually killing them.
This is a dangerous line to walk, and when things like critical hits or just plain bad luck get into the mix, an accidental character death is very much a possibility. Without introducing an additional mechanic, this leaves one of these needs unsatisfied, but instead it’s easy enough to introduce a new mechanic: Luck points. Rather than having death be absolute, we can introduce what is essentially a ‘lives’ system which can allow a character to come back to life if they are killed. This neatly solves our problem of accidental death, whilst still having death be something of a danger if we limit the number of lives that a character can have, forcing them to spend experience points from a campaign’s finite pool.
As an aside, we can also have Luck points have an extra purpose of allowing the players to re-roll potentially disastrous results, i.e. critical hits against them, but by making this a finite resource it again goes against party abuse. We can then front-load more mechanics onto Luck points like allowing extra actions and so on, but in general this serves as a nice barrier for the players to mess with the GM’s plans, which is a useful tool.
Significantly less dangerous than dealing with death, there’s also the matter of how else to show a character’s steady progress over time. This is the game’s ‘research task’ system, which functions in addition to the experience points given to the players, and allows the characters to slowly improve over time. This can be altered by many things such as having tools or teachers to assist in the rolls.
By ensuring that higher ratings are harder to achieve, this also gives a way for characters to begin to cover deficiencies that they hadn’t accounted for during character creation. In particular, the amount that research tasks can be conducted are improved by having a higher Willpower or Logic stat. These are traditionally one of the less combat-impacting attributes, and so this gives an opportunity for these characters to eventually catch up in combat, even if they initially begin a bit weaker.