Greetings,
This thread is not about homebrewing from whole cloth. It is about folks that take known settings such as the numerous ones from D&D, and IPs such as Starwars, Marvel/DC, Alien, Game of Thrones, etc.. and make their own content. For folks who do this, do you cleave as close to lore as possible? Or do you take the foundation and run with it? Universal generic system or custom bespoke? What is your process?
I am three years into a Star Wars campaign. With Star Wars as with comic books, the big problem is choosing what lore you are going to treat as canon. There are at least 3 possibly 4 periods of lore in Star Wars which conflict with each other and have required lore retcons, and additionally there are different levels of canonicity - how canonical do you treat video games? comic books? RPG settings? movies? TV shows? Is it all the same or are some more important than others.
My solution has been to treat the canon as if it was itself in universe "based on a true story" dramas written by Snivvian narrativists for the Holonets sometime after the death of Palpatine in the New Republic era, and as such it's as trustworthy as a Hollywood historical movie. Thus while the broad sweep of events and characters described may have existed, the details are not necessarily trustworthy.
Only what is in the game is considered fully canonical.
The following is considered highly canonical:
a) The original movies.
b) The "Han Solo Adventures" trilogy.
b) Andor
d) Rogue One
But keep in mind that everything that is fully canonical concerns events that are AFTER the date of the campaign in 15 BBY.
The following is considered somewhat canonical in that some of the lore from them may be correct but some of it may have been wildly misstated for "dramatic purposes" or because the dramaticist wasn't actually acquainted with the real events (such as what happened on Mustafar as no witness survived):
a) The prequel movies.
b) The clone wars cartoons, Bad Batch, Rebels
c) The Droids cartoon
d) Jedi: Fallen Order
e) Most WEG source books such as the Imperial Source Book, Bounty Hunter Source Book, Corporate Sector Source Book, etc.
f) The "X-Wing" series video games.
g) The Zahn trilogy
h) The first three episodes of The Mandalorian.
As examples of major departures from either official canon, the clone wars lasted 10 years in the game universe, Anakin was actually 15 rather than 10 at the time he started training (and thus Vader is 12 years older than in the official timeline at the time of the original movies, and Obi Wan is much closer in age to his padawan) and Darth Maul did die permanently before the clone wars even started. (The history got confused because Darth Maul's brother did at times pretend to be Darth Maul to intimidate and confuse others and this legend persisted in the historical narrative.)
The following is considered non-canonical BS with only vague resemblance at best to historical events
a) The Force Unleashed video games
b) The Sequel Movies
c) All Disney lore, novels, and live action not otherwise mentioned.
Within this very loose self-selected framework of what the Star Wars universe is really like I feel free to add and create as much as I like. It is after all a whole galaxy, fantastically bigger and more complex than even the extensive lore (perhaps the largest body of IP ever created) can cover. For example, the campaign is taking place in the Aparo sector and there are 120 or so newly inhabited systems most of which have never been mentioned in the lore much less described, of which the players have visited locations on about a dozen of them.
Star Wars requires a setting specific RPG for the following reasons: there is an in-universe narrative currency (access to the force) and there is an in-universe magic system and magic systems are notoriously specific to setting. For my purposes I'm using Star Wars D6 because I am familiar with it and enjoyed it back in the day, but I'm by no means convinced it is the best choice. On top of that, the WEG game lore is brilliant and is impactful to this day, but the WEG editing and product line oversight was minimal and incoherent at best (there appear to be three separate takes on how powered armor works, for example), resulting in almost no consistency in the published products concerning balance of races, equipment, creatures and star ships. Everyone did what they thought best with little in the way of apparent guidelines or oversight. The result is that almost none of the rules describing the content of the game universe are usable and I'm forced to produce almost all the secondary content.
Worse, while the core mechanics of D6 are very solid covering movement, combat, and skill use well, there was a very strong assumption of the core gameplay loop in the original game and everything they added outside of that gameplay loop was clearly not play tested and hand waved with a meta rule that the GM would just handle it in a cinematic way by fiat when the rules didn't work. So the original rules basically only work for Alliance commandos performing missions for the Rebellion, mostly on foot or (maybe) in star fighters or in cinematic chase scenes involving vehicles of the same scale. What that means is that if you get outside the gameplay loop chances are the rules are sketchy and will need to be revised if you don't want to be continually exerting GM force. This becomes really obvious if you are familiar with other RPGs. For example, Traveller has much more detail available for basic Star Ship operations even though we see in the original source material scenes that are about basic starship operation - Han rushing around needing a hydrospanner, Chewy performing maintenance on the Falcon in downtime, R2 being asked to lock down that deflector shield, or pilots being told to switch power to shields "double front".
And what that means is that I'm essentially doing the job of a product owner for the WEG product line and trying to clean up the poorly edited stuff that they made in the 1990s that I didn't really catch back then because we were staying on the happy path of being rebels and playing the published adventures which were on the whole really linear and even had things like handouts where you would read what your PC would say during scenes. That and coming from 1e AD&D I was much much more tolerant of balance issues then than I am now 30 years later.