Vedalken Eldricht Knight

[RogueJK]

I doubt my DM allow me to cast anything with a shield and a weapon in the hands without the warcaster feat

My post was talking about a Bladesinger specifically, which wouldn't be using a shield anyway. Even if you dip Fighter or Artificer, Bladesingers lose their Bladesong if they use medium/heavy armor or a shield, so they generally fight with a 1H weapon in one hand (as you would be doing with a Rapier or Shadow Blade) and the other hand empty, which means that other hand is free for casting without necessitating Warcaster.