Well you got core features, but you also have additional features that should've been in a game, if everything was optimal and the developers had unlimited time and resources. But that doesn't mean that the game is broken otherwise. Cause then Diablo 3, Battlefield 3, Skyrim, Half-Life 2, Farmville, Minecraft and more would all be broken games. And that's a pretty bold statement, if you ask me.

For me, "should" implies a definite requirement. There are features in all games that might have been nice, that could have been in a game, that would have been included if they had time. But saying that a feature -should- have been in a game, means that there was a serious flaw in leaving it out, rather than "it would have been nice if it had it."

Seems to be a good system to me. I can't think of any major downside other than the added complexity of working with the system.

One issue to consider is something that has already been mentioned in this thread. If you introduce this limited-save mode, you will inherently be introducing a new mechanic. The player will have to consider "Is this a good time to use my save?" Now, if you can balance this then it is all well and good, but you will have to try and consider how this will affect gameplay between the different modes as this is not going to be the default option.

The limited save mode could end up as a more relaxed gameplay option, simply because the player doesn't need to put the extra consideration in to using their save or not. With the semi-limited state, if you die and you end up losing a lot of progression, the player would get frustrated that they didn't use their save. If they use the save then go through a lot of simple progression before dying, they end up frustrated for having to replay a lot of easy areas and not saving later.

You need to make sure that the extra limited save turns out to be a relief, rather than a burden. If this isn't the only option for the save mechanic in the game, then it's even more important that you get the balance right.

Here's my personal opinions/experiences on these matters.

You are right, but you are also so very wrong. In Gothic 3, I had just cleared out an entire area of Shadowbeasts, Bisons, and two Dragons. I probably spent 30 minutes up to an hour to get this stuff done, and there's absolutely no autosave or quicksave in the game. Then suddenly, a bugged Wild Boar went through the mountain itself, because the pathfinding in Gothic 3 is absolutely horrendous. And Wild Boars had, early on, a bugged attack that was impossible to get away from, so they could sometimes spam-attack you to death, no matter how strong you were. Suffice to say that I was not very happy that day.

Personally, I agree that Quicksave breaks immersion because it's a conscious action.

There's definitely a quicksave in that game. If I remember correctly they often encourage you to save often (load screen tips). I really liked the Gothic 3 quicksave as it has 3 or 5 quick save slots, where you'll overwrite the oldest one. Much better than the regular just one (like in Skyrim). I quickly learned from Gothic 2 that it's a good idea to save often, and it's a good idea to use several save slots.
Going into the menu and saving does break immersion (particulary in Gothic 3 where it changed music track), but quicksave quickly develops into something reflexish. One advantage is that I decide when the game makes a sudden hiccup/lag due to saving. I disable autosaving because I really dislike unexpected lags in the middle of a battle.

But I'm all for Autosaving and I actually feel that any game that should have it and doesn't, are broken games. Personally, I prefer the consta-save of the Diablo series and of MMOs.

These systems depend on a respawn system which really makes a big change in the game universe. I would not find it immersive to respawn after death in the gothic games. There's no lore about it, and nor should it. Gothic games tried to be somewhat "realistic". It's not a game where 90% of the items are "magical". I don't think a respawn system would fit at all.

Crysis had normal save anywhere you want. In crysis 2 they changed that to automatic saves, which works smoothly because they made the open world, into a linear one, with it's "action bubbles". The game was very dissapointing.

One issue to consider is something that has already been mentioned in this thread. If you introduce this limited-save mode, you will inherently be introducing a new mechanic

Indeed. It was in farcry where I really really thought about saving. A big part of the game time went into replaying from an earlier save, just so that I could improve the situation in my later saves. I can't say I that particular part was very immersive.