I think they should and WILL have this in game. The fact that they are going out of their way to make sure that the game follows the core D&D 5e rule set closely and has everything that is in the Player's Handbook is the secret key. It has to to be able to a D&D game simulator. DOS Game Master mode was nice and was the first baby steps leading to this ... But I think ... they are going to drop that sweetness on us eventually that we can create and run our own games in BG3 in DM mode. Come on Swen Vincke we need you to drop that on us!