Peter David told me at a Vulcon convention that he didn't like the idea of killing Janeway, just like he didn't like the idea of killing Janos. However, he was asked to write the book and he knew if he didn't someone else would so he might as well be the one collecting a paycheck. I got the impression from him that Q taking Janeway was his idea, but I may have misunderstood. I do know he liked it ending that way because it allowed the possibility of her return.
He said he has received a lot of hate mail for killing Janeway and has told these angry fans that the decision was not his and that he wrote the possibility of her return. Apparently some individuals have written him some pretty venomous comments.