Oh God. I sympathise I really do. I have been in that particular situation twice and never again. I am very wary about internal politics in certain types of organisation and like to have a full overview of it way before commiting myself. If that's not possible I don't take the work.

I admit to liking waterfall myself (it suits the kind of work I do) and if well done by competent people and for certain types of project its the way to go ...