It speaks so well of you and your corporate culture that you're asking the community you'd like to reach, without making assumptions. In my opinion, you list table stakes. Excellence in attributes like flexibility and benefits are base expectations for qualified engineers with choices. What matters most to me when making a decision on how to spend my time: 1) the problems I get to solve, and 2) the people I get to work with in the process of solving them. If you highlight what is compelling about those two things then I think the right people will get excited and connect. Good luck and I hope you find great people/position fits!