(re: Why wasn’t Space Quest 5 a CD game?) SpaceQuest.net is definitely the best resource of Space Quest information. I’m sure Frans won’t mind if I quote his website to partly answer your question (maybe Ken remembers other things about this time and how SQ5 was developed at Dynamix instead of at Sierra) – this is in the Space Quest 5 section under the Funfacts heading:
Have you ever wondered why Space Quest 5 doesn’t have “voices”? After Space Quest 5 was released they were in fact working on it. Sierra’s Official Hint Book confirms this. It says: “Finally, 14 months after the preliminary design meetings were held, SQ5 was shipped to eager Space Quest fans across the galaxy. But the story doesn’t end there, The Next Mutation will be translated into five languages and converted to a full-voice CD-ROM version as well.” Sean Murphy, an artist on the Space Quest 5 project adds: “I can’t say for certain; I seem to recall that we had actually started work on doing just that [preparing a CD-Rom version of SQ5]. I think that politics and the fact that Dynamix was going through a very rough financial period at that time prevented us from doing any supplemental work on it… I suspect that the management was eager to move on to another “big profit” project instead of spending time and resources for a “gold” version of an already-released game.”