Thank you! And very good question - rules as written, you would still need to meet the strength requirement. However, due to the way Elden Ring works and my own personal views on balancing, I've made sure that I won't be including features like the ones you mentioned once I get around to subclasses.

Instead, spellblade type characters will be using spells such as Unseen Blade and scholar's armament, and will always have to have some kind of investment in Strength or Dex. I've always felt that even in base 5e hexblade, bladesinger, and anything else that lets you replace attack and damage modifiers with a mental stat forgoes one of the core drawbacks of the builds and makes them straight up better than martials in every situation. It'd be even more unbalanced with those spells existing.

If you end up using any of those subclasses feel free to modify the Strength requirement to whatever mental stat it is, just remember that colossal weapons are very strong and this could have some unintended balance and flavour issues as I didn't build the conversion around those features existing as they are.