Want to give a quick summary as well ad why it only takes 35% of the effort... though i haven't really seen any complaints around effort...
Rather than Bastion Points or upgrade time or anything like that, it's simply:
When the players level up, they can choose to level up their Stronghold.
When they do so, they pick up a Stronghold Upgrade (like a Great Hall which improves persuasion checks when you host, or a Hospital that improves healing checks, or a Monument that can be taken if a PC dies, after which the party increases their Spirit Die).
After they pick an upgrade, they roll on the Stronghold Encounter table. It's a d20 table, where "nothing happens" or there's a "diplomatic mission", or a "siege", or a "plague", or a "natural disaster".
And that's it. The similarities are clear between the two, but the SW version just gets to the meat and the fun stuff without the fiddly nonsense that adds next to nothing. Changing it to 5E would basically only involve going through the upgrades and making system-based adjustments.
Edit: there is another twist that you can add, which are the "Advantages" and a "Complication" for your stronghold to give it flavor.
An Advantage (a good thing) could be your stronghold is in an exotic location, it produces some kind of item, or there's a mentor that lives within.
A Complication (a bad thing) could be that your stronghold is Contested (there is an invasive species that is a nuisance difficult to root out), or is well-known (your enemy knows about it), or has a dark history (foreboding).