Use Stalwart as you would a primary. It becomes viable if you bring a Supply Pack and supply yourself with ammo. The issue then becomes that you don't have a "support" weapon, so you'd have to sub your primary for something that may fill that role, such as the slugger for armor for example. With the new warbond, this build becomes even more viable with the grenade launcher secondary.
Now that's an interesting thought, I hadn't considered how explosive medium armor penetrating primaries could make Support weapons that focus on crowd control more viable as you have alternatives for addressing medium and larger enemies.
Right there's only a few support weapons that have medium pen and they're low capacity, so if that's your niche a more generalist support weapon might bring you better mileage.
I use scorcher/eruptor/dmr etc as the backup and stalwart+supply pack as primary. Setting the stalwart to the highest rpm is plainly awesome for suppressing bots and shredding chaff.
And now with the new supplies upgrade those 4 boxes on the backpack last me way past the cooldown for a new pack