Perhaps because it can help prevent player errors from accidentally putting on the wrong mutagen/enhancement and not realising it until later? And because it doesn't really make sense why you can't change out enhancements for armor/weapons; just rip out the offending portion and replace it, or melt down parts of a sword and re-inscribe new runes onto it.

A patch doesn't need to be restricted solely to fixing bugs in the game; the changes to mutagen drop ratio and Quen in 1.3 are ample proof of that. CDPR have shown themselves to be receptive to player feedback about what's not working/not fun in a game when making 1.3, so I'm just putting my ideas out there.

Heck, maybe this could be a change that's difficulty-setting specific. On Normal and Easy modes, you can freely change out mutagens/enhancements, but on Hard and Insane, once applied, they're there forever.

The problem is that there are items in the game that are entirely useless - all non-greater mutagens. They even have a somewhat negative effect, because if somebody who doesn't know better actually uses them, he'll regret it later. This makes no sense from a game design point of view.

Obviously, the two possible solutions would be 1) to allow the player to combine lower-level mutagens to make better ones or 2) to allow the player to upgrade his mutagen slots with a higher-level mutagen of the same kind.
Second option would work better, since it allows the player to use the whole "mutate" feature once it becomes available, instead of waiting for his first proper mutagen to be finished.

No. That is exactly what I meant by the excessive character optimization that was not designed to be an objective of the game and indeed should not become an objective of the game.

Use enhancements when they are useful to you. If they are not the "best available in the entire game", so what. Holding out for only the best is character optimization of the kind that I do not believe the game should encourage.

How does "allowing the player to freely upgrade/swap enhancements" translate into encouraging character optimization though? It seems to me to be more a question of playstyle than anything else. If a player is the type who's not interested in min-maxing, then he will throw whatever mutagen he has available into the slot and never look at it again. (Or even not bother with mutagens altogether.) If a player IS the type, then he will hold out for "the best" anyway. And aren't people already writing "optimization" builds for TW2 with regards to ability selection when levelling up anyway?

In any case, however a player decides to play his Geralt has absolutely no impact on anyone else's gaming experience, so I really see no harm in allowing players to swap out mutagens/enhancements. It's all up to CDPR in the end though. I can live with hanging on to my enhancements until I get "the best". ;)

More DLC/quest for Chapter 3 please. I really would like to explore the area outside the gates.

If it was the devs intention not to have "excessive character optimization" in the game, then this whole mutagen feature was a mistake, and should never have been implemented.

I'd also like to know what you believe to be the opposite (or rather, the better counterpart) of "excessive character optimization", since that whole idea doesn't make any sense for me. Any kind of character development is always character optimization, one war or another.
What behavior do you think the game should encourage? Just putting the first mutagen you find into any empty slots you have, no matter what it is? How should a player be encouraged to "optimize" his character by selecting the mutagen that best suits his preferences, but not by making sure he uses the best one available?

It's excessive character optimization when the business of finding artifacts to "improve" your character becomes serious enough that players not only demand changes to the designed characteristics of the game solely for the purpose of maximizing the statistics of their character, but dismiss the game as broken because it does not allow them to do so.

If it were absolutely necessary to change an already acquired and used enhancement to complete some part of the plot of the game itself, I wouldn't consider it excessive optimization. But merely demanding that you be allowed to use all of the best armor, or weapons, or enhancements in the game just because you want to min-max your character is silly, and the game developers should not compromise their own designed balance of the game to accommodate it.

This is especially true when the developers are resource-limited and have better uses of their time than to satisfy min-maxers just because they want to play games in their habitual way.

There's not a single part of character development that is "absolutely necessary" to complete some part of the plot, so I suppose that all of it is entirely undesirable to you?

"Maximizing the statistics" of your character is already possible, and has been possible since version 1.0, so that's not the problem. The problem is that the game gives you loads of items that are entirely useless or even harmful, while they are supposed to be useful. The problem is that there is a feature that is realized in such a way that it reduces itself from something that enhances the gameplay experience throughout most of the game to something that plays a minor role rather late in the game.

You should keep in mind that the game is supposed to adapt to the player, not the other way around. Or, in other words, if you like this feature in it's current form because it forces everybody to play the way you like best, that still makes it bad design.

On that, we can reach no agreement at all, because I believe that statement to contradict the intent of the game developer to create a game that offers a particular experience, not merely to conform to the habits of its audience.

There are a lot of good suggestions posted here.
I would like to add my minor request:

Please make the it so I can easily shove the children out of the way like I can with the other town npcs. There has been a number of times when children start following me around town and they get bunched up behind me when I'm in a narrow alley or behind a pile of crates and they won't move. I tried re-logging and they are still there. The only thing I can do is reload a earlier saved game to avoid the whole thing.

The same problem also happens with the dwarves bunching up behind me in the mining tunnels during the "Hey, Work's on in the Mines!" quest. This is especially annoying when Im trying to get away from the dying rotfiend before it explodes.

Oh, now that's something new. Any arguments on this one? Or is it just because you claim it to be the right way?

The whole point of a role playing game is that it is INTERACTIVE. Meaning you make choices and control a character and play the game; this goes doubly so for a role playing game, where you the player play the game along a certain role.

If a game whose major characteristic is that you can play it the way you see fit, punishes you for your play style, or unduly rewards some other play style, you break the intended goals of your game.

Non sequitur: your conclusion does not follow. Just because you interact with the game does not mean that you should play it just as you see fit. You interact with the game within the terms of the game, which were set forth by the developers such that they offer a certain experience and not just any experience you happen to want to have.

What's wrong with using the mouse, it's pretty easy to get the target?