If there is anythign in this game, that needs better open world content, then its Skellige islands.
The games absolutely most rushed content of all, aside from the games cobmat and character development system that didnt got looked enough at.
Made for that already plenty of suggestions, how the open world coudl get improved, especialyl skellige and the basics for that are very simple_:
1) Reduce the Siren Orgies there by half and add alot more enemy diversity to SKellige, add Sharks as beasts, add Ghosts Ships as some kind of "water monster nests", replace them illions of smuggle nests with more ship wrecks, with underwater caves/ruins because not all parts of the sea must have been always a sea in the past maybe... add reavers/pirats and also huge usea monsters like sea snakes and a kraken as enemies there
2) add there also more druid enemies and so, not all druids must be friendly towards geralt, especially not after two specific events there that ruined the nature... to have also more mage like enemies in this game, which it has sadly way too less, instead only 99% of the tiem soldiers and archers..the very first and only mage enemy that you fight agaisnt is in HoS that one Ophiri..really rediculous to have in the whoel game just one single mage enemy .....
Make also Dryads return (Morenn)..Skellige woudl be a good place for them
3 Let the Vodyanoi also return as another option to make the enemies around and in Skellige Sea territory more diverse (also i nToussaint) because thats the region whey they live and where we met on them also as well in W1)..but more of them could live naturally in other regions liek Skellige in some kind of atlantis similar town or so under water
The plans for this game surely weren#t overly ambitious. WEhen you played through the game ect. and see that they dropped the support for this game after 2 expansions basically and the game has still tons of wasted potential for more content, then you must actually say that CDPR either massively lacks in the interest of making this game better, or they lacked from begin on the vision for this game,, because they planned already for this game ahead to be supported only for the 2 years of development time ect until B&W is released, and had for the rest of this game no vision.
Good games have vision,s how you imprive them and add content to them for more than just 2 years, you plan ahead for at least 10 years when you have created such a good vanilal game, that offers easily the foundation thats needed to add more content for it for the years to come...
But instead CDPR decided to throw witcher 3 now for a whiel firts into the dust ,so that they can work on their new IP Cyberpunk 2077... a game, which has a great risk, that it can eventually flop, while they have with the witcher series already a strong and dave powerhorse IP, that is incomplete and could offer alot more great content still for many more years (thats how I do see it)
Its really sad too see, how extremely underdeveloped and not very well and completelythought out the design of Skellige is, compared to Toussaint, which looks like a sparkling diamond compared to Skellig that is full of life and diversive life....