I haven't gotten into the nitty gritty of designing it, more just conceptualizing at this stage, but my own game is going to be taking cues from Arora: Age of Desolation. Thats a 3PP supplement for 5e DND, and its a real hidden gem.
For one, just to comment on it, Arora is probably the first time Ive read any RPG material where it felt like I was just reading my own thoughts, so while that colors why I got so excited by what Arora offers, it has actually played well in practice, not just for 5e but even DCC and Black Hack.
But as for what it does in regards to home bases, it frames their creation around the need to make Survival more of an interesting and fun experience overall, and moreover one that works even into the higher levels.
But its not just home bases or Strongholds, its entire Settlements, which scale up from big tent camps all the way up to Megaopolis sized cities, and where it really excels is that it keeps it all very manageable and non-fiddly, though it might be a little too un-granular for some; if ACKS is at one end of the spectrum, Arora is nearly its opposite.
The way the system works is a sort of step-by-step thats integrated with the supplements Exploration rules (which are also fantastic), and you go through the process over time of finding a good spot, attracting settlers, developing it and establishing infrastructure, and then the gameplay loop kicks in with the need to protect the Settlements, which provides a necessary drain on resources so that theres generally always a reason to go out and adventure.
The way my game is going to be adapting it is by extending the bookends of the progression (the camps characters make to rest through the night are going to be at one end, and entire nations at the other end), and then integrate with a more elaborate take on ACKS idea of having class-specific Strongholds and Organizations. This would then result in the Party becoming the "Alliance" as the players variously build up these large scale power bases, and through these, high level play transitions into a morphed, larger scale version of basic adventuring.
A thief in normal adventuring might use their skills to pick a lock or subdue a guard, but as part of the Alliance, their Guild will be fostering a shadowy crime-underworld, undermining the Alliance's enemies by cutting off their resources, blackmailing or otherwise scamming people on a large scale.
Its pretty ambitious, particularly given I intend for the game to cleanly scale between individual adventuring and the Alliance gameplay, as well as allow for players to cleanly and freely swap between the two at will, but its more or less what I see as ther logical conclusion for these kinds of mechanics. Plus, its also pretty important as one of my goals for the game is for reaching a high level to not be a reason to stop playing and start over.
ACKS got close but never really went far enough, and it really buries its good ideas in a lot of minutia that, while useful, tends to obscure the gameplay that makes it all worth it. Its really a book that could have done with segregating that stuff into a separate book, so that the player facing stuff could be cleaner and more concise.