Honestly I feel that having character-progression in the witcher games seems forced into them "because RPG".
In my opinion, the way leveling up worked in both previous games was hugely detrimental to the game, for example TW1 would have you repeat 2 animation cycles for each style throughout most of the game, only towards the end would you have a unique animation cycle for each step of the combo.
TW2 forced players to play the combat in the most boring way imaginable by making you unlock essential abilities that Geralt should absolutely already have.
Giving the player access to all of Geralt's combat abilities and moves from the beginning would only make the game consistently interesting as well as fit better with the lore, rather than boring you to death by forcing you to dodge dodge dodge dodge dodge dodge dodge attack dodge dodge dodge etc.
If you want character progression, the way it should be done is to improve the abilities Geralt already has, NOT lock them away from you.
For example:
Deflect arrows -> Reflect arrows
Riposte -> More powerful Riposte
Actually I think that while the "problems" you mention are valid, the reasons for why these problems are there are not.
If you have all skills and abilities unlocked from the start, you know whats going to happen? they will all start to get boring quicker and simultaneously from the beginning, by the time you reach mid game or earlier it will all be discovered and feel mundane, common, nothing of any particular value.
If the beginning seems uninteresting, or not fun, and you dont like having to see the same 2 animations in TW1 for a long time, thats because firstly they werent well designed, and secondly the progression's interest curve was unbalanced.
If the combat in TW2 would be fun from the start there'd be no issue at all, and it would only get more fun as you unlock stuff to keep it fresh, while you learn how the newer things change the value and use of the old things, and just like that, TW1 shouldn't have had repetitive and boring animations at all, beginning or end or mid game or whatever.
Lore problems are another story, which i can agree more with. It all comes down to where you want to distribute the value of skills and moves, unlocking a more powerful riposte is much more boring than unlocking riposte in the first place, out of not having any similar moves before. There are many solutions that can be done but at first glance, without being the designer of TW3, if the game is aimed to last about 100 hours, then unlockable content probably would have to be seriously meaningful and important.