Great question, and let me first say you are not alone. Unfortunately many organizations do a poor job of communicating and disseminating information. Now the good news...that doesn't have to be you. While more challenging, there ARE ways to communicate up. A couple of suggestions:
1. As a team of middle managers, identify and prioritize a list of relevant and important points that you would like to convey.
2. Put together a plan, not just points, but identify how easy they are to implement, what resources are needed, schedule for implementation.
(Note: my teams used score cards in an opportunities matrix to convey the relevant message)
3. If you can identify someone on the leadership team that does have an open door policy there might be an opportunity to, in a positive light, communicate that the team as a whole has some ideas
I am sure your ideas are great, but ideas with a body of peers and a substantive plan are forceful. If at the end of the day you put together a tremendous plan and it isn't considered, don't worry, you did your part. Take that lesson forward and never forget it.
Oh..AND you may have outgrown the organization!
Hope this helps Tristan, keep up the great work.
S.E.