How you could use qualitative OR mixed-methods design to write a proposal for the hypothesis:

If peer-directed interventions/peer mental health support programs and family support are made available for veterans and first responders, will there be a successful reduction in stigma barriers pertaining to mental health?

Outline how you would design a study giving as much detail as possible about which design you could use.

Who are your participants? What are your measures? What is your procedure? How would this design help to answer your research question?

Consider the potential value of having the control group receive some type of generic "placebo" intervention as opposed to receiving nothing.

Even though this is hypothetical, be sure to contextualize it in a real setting with an address. By including a description of the site, your audience is better able to understand your methodological reasoning for choosing that site over another.