How do I propose my own project?
First check whether your activities can be performed under an existing project. The list of projects is continuously growing, covering a wide range of research topics and product ranges. The Eclipse subprojects are overseen by a project management committee (PMC). If you have compelling reasons to start a new tool or technology, contact the PMC of either the Eclipse Tools Project or the Eclipse Technologies Project.
Having a proof of concept definitely supports your arguments, of course. Furthermore, before you contact the PMC as an individual, it does not hurt to first find other people and Eclipse Foundation members who would like to collaborate with you on the project. If interested in your project, the PMC will guide you through the steps required to establish it as an official Eclipse project.