"Ask existing users if they want this feature" is a bad idea because users are going to say "yes" to everything, especially in a B2B SaaS app. It means nothing.
There's some very obvious ways to prevent that. One way is "here's a list of ten candidate features we might prototype this week/month/quarter/release, but you can only pick one". Or ask users to rank them, and only pick the consensus #1-ranked. The ensuing dialog can be informative.
Have you never say "no, I don't care about it" when asked such a question? I say that a lot of times, and get that from users all the time too.
The thing is, you can't confuse a "yes" with the user actually wanting it. But there are plenty of ideas that everybody clearly do not want, and people will answer you a "no" if you ask.
