Two Scottish writers I really enjoy are Stuart MacBride and Denzil Meyrick. SB's Logan McRae is a great character, on a par with Jackson Brodie in my opinion.
Another wonderful Scottish writer is Chris Brookmyre, several of his books have the same main characters, e.g. an investigative journalist, a counter-terrorism policewoman, a private detective (not all in the same books, each character has their own set of novels). He also writes stand-alone novels, the themes of which are varied, but always very funny, and very dark. His writing has been described as Tartan Noir.
Also, have you tried any of Reg Hill's Dalziel and Pascoe books? "On Beulah Height"is one of my favourite books ever.