In their defense, Larian already made huge-impact changes in the past (even for bg3, they changed the style of the narrator and the initiative system once they saw these were not popular after the gameplay demo last year). I agree that for tweaks like these to be more easily implemented devs have to plan their coding structure accordingly from the beginning so it allows to alter stuff (it might not be impossible but definitely harder to rewrite the code to work on a specific way retrospectively). However there was an Gamasutra interview with their lead systems designer and i quote what he said according to the interview, this is what keeps me optimistic:
"My advice would be to be prepared to throw away your design docs on at least some of the features and to respect the process. I think if the studio is doing Early Access, they need to realize that this really means that the players can give you feedback that does not align with your design vision at all. And you will have to reconcile that. But doing that will actually make the game better for a lot more players as it turns out. So my advice would be to be flexible, design wise, and to plan your design ahead in a way that is kind of modular. This is something we got a quite a bit better for this project I think. We have plans for systems that we foresee that we'll have to add due to new classes, new features, things that we haven't talked yet about. But we try to make sure that all of them can be swapped for something else that the players will say is really a priority for them, or can be changed in a way that will not make us remake everything from from the get go. So we try to keep systems kind of modular. Flexibility is really the key here."
They have a lot of time to alter things still (and thats the purpose of EA) and a couple of mechanics as they are now in EA are not fully functioning (and it might be on purpose). I have a feeling that the spammable rest mechanic is just a placeholder as during one of the Gamespot interviews from June 2020 Swen said "because of the way that the world works and how dungeons and dragons works its not always safe to long rest, there are zones where its unsafe, so if you are in an unsafe zone the only thing you can do is a short rest." What i can think is that they wanted to test out companion interactions more effectively so they just left it without restrictions for EA. Similarly i heard somewhere they said they already work on options to alter the RNG but they wanted to go full-RNG for EA on purpose just to see how the crowd reacts.
So fingers crossed they are listening and design their systems cleverly. I know mods can fix things but i have a mixed experience with those (I use mods but not on my first playthrougs), usually they rarely work with each other and not always up to date so here's hoping we have a couple of official toggles for the ruleset and difficulty in bg3. Im okay if not all of these are part of EA testing because i see how multiple versions of the rules could mess with their statistic and feedback tools but i hope they at least do a community update about their approach on this topic.
Holy hell, I sure hope this is accurate stuff, and that it aligns with their current philosophy and plans! =)