realistically, going real time with pause is likely to cause fairly fundamental code changes and as a result there would be significant development overheards, that's just my opinion as a software developer myself.
I think you'd be looking at either: 1) adding a much longer period to early access 2) needing to cut other planned features to fit it in
Those are decisions any business has to make on a regular basis, and it'll become a cost vs reward thing.
issue with making early access window too long, is the hype of the game will absolutely die, which may not be an issue if enough people already bought into early access to justify the production of the game, in fairness. However, if the buy in hasn't hit whatever targets Larian and Wizards have, there will be a stronger need to not have the EA last too long. A year seems to be the length most people anticipate right now, for all we know, Wizards might want a shorter window than that, it'll depend as much on what contracts are in place between Larian and Wizards as much as anything else.
Cutting content to add RTwP? That is risky because the result could be a game with far less actual content, which could result in negativity toward the game as well. Chances are, regardless of if you prefer turn based or RTwP, if you're hyped for a new baldur's gate that is "based on" 5e rules, you're going to get the game and probably play it (at least partially, most people dont finish games these days apparently) and they'll get your money either way. I'd have bought it whether it was turn based on RTwP. I am happy its turn based personally, although i think enemy turns could be sped up. I'd have preferred a more faithful representation of 5e rules (Solasta absolutely destroyes BG3 right now in this regard tbh), but I'll still play it either way. I just am unlikely to bother with it outside of the main game in the way i might have if it was more faithful to D&D 5e.