I'll just add some additional perspective / food for thought.
I tend to go the opposite direction - making everything as open as possible. It opens options for people modding your game and messing around with the files in all sorts of ways that can actually be beneficial to the longevity of the game, and by extension, you. I actually went as far as making sure that just about every module in my upcoming game is externally defined and works together independently of each other. So, NPCs, items, spells, quests and dialogues are all external files that are easily human readable, and not defined in game. This means that;
Someone could add an entirely new file to define an NPC that never existed. They could then add a new dialogue file, which points to a new quest file, which rewards an item based on a new file as well. Now, you have an entirely new NPC, who gives you an entirely new quest through entirely new dialogue, rewarding you an entirely new item. Essentially, short of efficient handling of external graphics and a level editor, this enables people to pretty much make the entire base game (or entirely new content in the same style) with the game's own resources.
It also opens up for fans of your game making new languages available, by simply translating the existing files, and if your game is setup to dynamically detect new language folders, you can suddenly have fan-made localized version of your game that didn't exist before.
Lastly, a little anecdote;
After we released our first commercial game, there was a bug that unfortunately made it so that some people's savegames didn't register a certain change. I of course patched and fixed this, but until then, I could write up a manual quickfix, instructing people on how they could easily fix their own savegame by hand via a few short steps. I could then pin that in the Steam community or where ever relevant, and people would be able to easily fix it before the patch was even deployed. Now, I'm not advocating this as a get out of jail free card for sh*tty coding (such as what I did), but this wouldn't have been possible if I had opted for a closed save system, and a lot of people were actually happy with how quick and easy it was, and that they didn't have to wait for a patch if they wanted it now.
TLDR; As long as it's strictly single player (and there are no MTX or other such factors), the way I see it, there are far more benefits to going as open as possible, as opposed to the other way around.