Maybe Shatner and Stewart themselves would be the best advocates for such a project. Shatner is famous for squeezing every drop of juice out of his own career, and this would be another project that he could easily sink his teeth into. Since he is already familiar with the source work and has done some live readings at Comicon (thanks for that, @JD), that would be the most likely option. Stewart, probably not so much. I think he's more likely only interested in "significant" projects to further his career. I don't think he's quite as ... "prolific" ... as the Shat-man when it comes to such things. No facts there, just a best-guess opinion based on past behaviors of the two individuals in question.