Gameplay
Content around the principle of character development, it would please me, again seen from old school time, for the classes to have schools, orders, halls and there then trainers who want to be paid and one is sent for new skills on tasks. In addition for mages still tasks to bring back new spells from crypts, fortresses, dungeons, etc. to capture, or first assemble from parts.

The trainers have different locations and are logically distributed in the world according to class.
That is, you won't find any druid trainers in the city, and rogue trainers can be found in the city in the thieves' guild, which you first have to get into via story and in-game tasks.

In addition, I would like the specializations that you do not simply choose them, but in the game about story, his deeds, found places, etc. before the choice is made and decides.
This has a lot of potential for a nice amount of story around the classes and also takes into account the play style and choice of main class, which creates a lot of replayability value.

A budding mage who wants to be a necromancer won't find this in the mage tower, but should rather hang out in graveyards and make friends with the graveyard guard there.
And if you want to be an assassin, you'll have to eliminate people in an ice-cold way before you even get the choice, if someone becomes aware of you and your deeds. So shift some authentic good and evil behavior to the class choice as well.

Or a hunter will first have to track down his trainer himself in the wilderness and only then find a hidden camp with people who live in the wilderness and collect trophies etc.

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Story
When it comes to story, I always like a separation at some point into good and evil and the player has to make a choice.
Then there are completely different specialization classes per side and completely different storylines, places and tasks that you can see and get.

That means you can play through the game at least 2x just because of the separate storyline and the completely different feeling and then there are the many different class specializations.
So a lot of stuff and a lot of chances.
It does not necessarily have to be only good against evil in the story.
This can be touched on here and there in addition to the main story.