Alright... rephrasing the question:
You are a tadpole in Swen Vincke's brain. No one knows you are there. How do you steer the direction of Larian's plans post-BG3 in your desired direction without changing too much such that you are discovered?
(Please have an answer that is more creative than "No, I won't make a game like Baldur's Gate 3 and I'm cancelling anything that remotely smells of it.")
Edit: Wtf do you people like? WHAT DO YOU WANT?
I would buy the studio that made Solasta and then would build upon their engine for the next game.
I don't see how in the long-term Larian can't incorporate mechanics that people loved in Solasta into their future games. Not necessarily saying they (Larian) are or aren't, or that they should or shouldn't, but the Solasta devs don't have a patent on reactions or on flight. I mean, they're not splitting the atom here. While a purchase of the company could be a good move, I think it's just as feasible for Larian to see the main critiques of their game today, and improve upon it in five years (because "the engine can't handle it" has taught us that they certainly can't make major improvements now or in the short term). If other games outperform their own, or if they just like a mechanic in another game, they could easily make modifications for the next iteration of the engine. Or for a new engine. I'm pretty sure whatever is after Baldur's Gate 3 is far out, time wise.