This is the draft of the SAG agreement with Hollywood. Obviously the agreement does not apply to videogames but figured SAG is going to go for a similar deal with the video game industry. In terms of relevance is the AI part which is item 29 on page 60.
https://www.sagaftra.org/files/2023%20SAG-AFTRA%20TV-Theatrical%20MOA_F.pdf
I know there is a disdain for AI voices but I can't help but think that having a Lance AI voice for Sylens could work. Assuming an ethical deal is arranged that keeps Lance's voice with his estate and they are paid fairly then we should be good on the IRL front. And on the In-game front knowing Sylens he just seems like some one inclined to use some voice synthesizer if he was to lose his normal voice box. Add the fact the AI generative tech is bound to exist in Horizon anyway, and well, there is an excellent lore explanation as to why Sylens sounds the same, or the same, but off