The Gremlin gunline is definitely the way to go. When you add pigs, the warband has competing objectives in terms of play style. The pigs want to rush into combat but the Gremlins want to stand back and shoot. And then neither gets accomplished.
Mind you, its highly likely I haven't gotten the hang of Somer. As much as I liked the guy, I still think planning a warband around having your guys die is a daft idea. If you're going down the gunline route, I can't vouch for Opheila enough. She negates the gang's biggest weakness (Whoops) and gives you 6 more soulstones onto your crew.
As for buys with Somer, I'd say a Mossie (flying then using Pull my Finger is glorious) or Pere/Rami to deal with hard stuff.
And more Gremlins naturally.