If you really want to get the company's attention, don't picket.
Instead, host a mini "job fair". Rent a conference room or a hotel ballroom. Ask some of the other regionals that pay better and LCC's to come and interview Mesa pilots on site.
Could you imagine what would happen if Piedmont, PSA, Envoy, Allegiant, Spirit, and Endeavor all showed up and hired 200 Mesa pilots in a single day!
Have letters of resignation already typed up.