I know the Wizard class has a lot of subclasses already (arcane traditions) because of the specialist Wizards. However, they are largely the same with just different bonuses basically.
The Bladesinger is part of the Forgotten Realms, so it would fit this game perfectly, and it plays very different from the other Wizard Subclasses. This would be a wonderful addition to BG3 that seems like it would fit a video game even better than it does table top. If there's any hope of adding subclasses beyond what's in the Player's Handbook, please consider the Bladesinger.
