A life paths system doesn't need to be mechanical. The power of the life paths system in Traveller, is that it creates characters who are like people, not story characters. It's terrible if you're the kind of person who wants to tell a specific story about a specific character, or if you are really into the metagaming aspect of chargen. However, if you're really into experiencing another life, the simulation of another reality as such, it is pretty impressive. So, because it isn't really about the crunchy character-building metagaming, those metagame elements aren't actually very important to the system. (Traveller incorporates them for practical and simulationist reasons) Thus, a life paths system can be generalized as a back story writing tool. If generalized as such, it could theoretically be applied to pretty much any system.
However, a life paths system is restricted to setting. You can't really use the Traveller system to write the back story for a game about medieval diplomats, can you? It's rather deeply entrenched in its sci-fi genre setting, with star ships, and aliens, and interstellar empires, and such. So, unfortunately, you're going to need to either make up a lot of genre related details, or build a life paths system that is so generic that it leaves much up to interpretation. (Instead of "you join the space marines", you get "you take a military career path").
You'll also need to consider how far back the life path system starts. Does it begin with character birth, determining gender, race, social status, and even family history? Or does it let you choose some of that and start later on down the line, like when they begin education, or reach maturity, or choose a career? Does it choose your career for you, or do you have some say in the matter? How much input do you, as a player, have in the process? Also, how far does the life paths system go? Is it possible for a player to just play our their entire character's life in the life paths system if they choose to never retire? Does it always end when the characters reach a certain age? Or immediately after they choose a class and become level 1? (Or some other mechanical contrivance) Finally, you need to decide what kinds of characters the system can create. In general, you want the system to make characters whose stories will be relevant to game play. If it is too broad and makes lots of characters who are pretty dysfunctional in the game, that won't work out well for you.
Once you have a system that can create the kind of experience and characters your game needs, then you can go back into the system and work in those mechanical aspects of the chargen process for your game. You'll want your system to replicate the effects of the original chargen system as much as possible, so that your life path system doesn't interfere with balance.
Finally, and this is absolutely essential: TEST PLAY IT A LOT. Before you actually go and use this thing, give it a good 50-100 test runs. Make sure it doesn't create impossibilities, like men giving birth, people marrying themselves, characters arbitrarily getting younger or aging at different rates, people having siblings of different species from the same parents, etc. Also, test it to make sure that it always makes a full and functional character. Essentially, these things are really prone to bugs, and you need to catch them before they appear in play.