This save system would have multiple types of saves, which has the downside of complexity, but the advantage of handling most player use cases. They are as follows:
* Autosave: When you reach a save point, you are fully restored, enemies respawn, and the game is auto-saved; this save can be reloaded as long as no other autosaves have taken place. (Possibility of more than 1 autosave slot, with them being rotated, to allow reloading in case of an accidental save point use.)
* Standard save: Only possible at save points, but intended to be the primary means of saving. The game is balanced with this sort of saving in mind.
* Suspend save: Can save anywhere, but doing so will exit the game. Reloading this save will delete it, so it can't be used to reload if something bad happens.
* Assist save: Only available if the Assist Mode option "save anywhere" is enabled. Can be done anywhere, and can be reloaded. (Possibility of adding quicksave/quickload hotkeys for this mode.) Intended for players who prefer save anywhere, or those who want to use saves for practicing specific parts or just revisiting parts they like that happen to unfortunately not be near a save point.

How does this approach sound?

Edit: Why the low rating?

feels like twitter or instagram
why should we care what is your ideal save system is?
I dont get why you need to post these topics which are all about you

I think you lack the possibility of an Ironman mode. Ironman adds intensity to a game and ups the stakes. It can make a game comes alive and thrive. It can lead to real heartbreak when you lose everything.

But aside from that your system seems fine.

Stopped reading at "respawning enemies", total no-go for any serious game.

More options = better.
Ideally in a decent menu/UI (+shortcuts), and not in one scrollable page with a gazillion items (or text file, registry entry, console).

Good idea, but I'd have this as default if you quit the game. So, no option to do it, but quitting the game triggers it. It's sort of like an "autosave on exit" but separate to the autosave slots.

Maybe if there was a system where players would choose a Save System in the beginning. I believe this approach would be a permanent choice which would affect the gameplay rewards in various ways and would be simpler for the player to understand.

But I like your idea of options in-game allowing players to change them on the go. This would be really complex to develop, though, like you said, and probably people would find it rather difficult to manage.

Maybe, but:
* That would not be the default option.
* The game would not be designed or balanced with this mode taken into account. (In particular, having enemies (both normal enemies and bosses) that could easily defeat a player who doesn't know how to defeat them, perhaps because the usual strategy triggers a counter that wipes out the party, or perhaps the player is not supposed to go that way yet, would not work well with an Ironman mode for a first time player.) But how else am I going to level up that character I just recruited or class changed midway through the game so that they're on par with the rest of the party?

(The lack of enemy respawns is my biggest complaint about MIght and Magic 4-5: World of Xeen, with the second biggest complaint being the lack of damage numbers.)

That's one of the reasons to add that option to the Assist Mode settings (also to make clear that the game isn't balanced with it in mind while still providing the option).

Characters you recruit should automatically be of the same level as the rest of your party (but allowing you to adjust their skills manually if you so desire).
If you're dual-classing or changing class mid-game, you just have to live with the consequences of that choice.

Anyway, respawns aren't always bad...Albion, one of my favourite games, had respawns, but ONLY in wilderness areas, not in dungeons. And respawns shouldn't be linked to the save system in any way.
Also, grinding should be optional, not a requirement for winning the game.

From a resource management perspective, if it's possible to rest (or equivalent) in a dungeon or leave and rest/restock, the enemies in the dungeon need to respawn, to avoid a situation where the player clears out all normal enemies in the dungeon, leaves to rest, then trivially reaches the end of the dungeon at full resources, making the boss fight easier than intended.

The reason for linking respawns to the save system is that rests are linked to the save system as well, and it makes sense to link a respawn to a rest.

(The term "rest" refers to any cheap or free way to restore your party's resources (like HP and MP). This includes going out of the dungeon back to town to rest up, and it also includes things like being healed for free at a save point.)

As for the "grinding should be optional" statement:
* I don't really agree with that, to be honest. Games like Dragon Quest 1 would be trivialized without that mechanic (and I note that remakes of that game are considerably shorter than the original because they drastically increased XP/GP gains; you can see this in speedrun times, where remakes can be beaten in under 2 hours, while the original version (actually US Dragon Warrior) takes over 5 if RNG maniputation is not allowed).
* What you refer to "grinding" can be quite fun, and I'd rather not have that taken away..
* The problem with having new recruits be the same level as existing characters is that then you don't get the rapid level ups that you get with a new level 1 character fighting stronger enemies. I think it would be more correct to say that things come up that are more important than the game.

There are some good ideas there, but in general I hope the save system is not used by games as some kind of difficulty modifier, like that in harder difficulty levels you can save less or not at all.

So I rather prefer unrestricted saving, even if I don't necessarily mind if you can only save at save points or between missions, but I feel usually those are created due to simplicity and technical limitations (e.g. save points in older console games), rather than a way to make the game more difficult.

The idea is that Assist Mode, while it could be used to make the game easier (especially if you look at some of the other possible options, like double damage or health, or even invincibility mode), is not a difficulty selection in the normal sense. Furthermore, each assist mode option would be independent, so you can enable save anywhere without enabling any of the other options.

Also, one approach a few games use, but which really should be more common, is having custom difficulty settings with more fine-grained difficulty options. For example, in Fell Seal: Arbiter's Mark, you could set the difficulty to a high preset, but then take out the injury system or deny the enemy the ability to revive. Or you could set it to easy, except that enemies come with a full load of equipment, and the extra/elite enemies that normally only appear on higher difficulties do appear. More games should take this approach.

Then limit resting in dungeons, block returning to town after a certain point, or make the finale consist of a series of interlocking fights without intermission, so rest isn't possible.
Or don't even have "boss fights", they're not necessary in every dungeon imo.
I also don't get your point about "rapid level ups"...if newly recruited characters are always the same level as your party and you can manually distribute their skills, there's no issue imo.