I'm not a numbers guy, but I suppose one could build a canine companion PC without too much tinkering- at least in v2.2. Most of the abilities for humans could be applied to dogs (e.g. Charisma = how sociable the dog is) so one could distribute Attribute points as per human char-gen. Then, determine a reasonable number of Skill points based on the dog's age and then distribute them to skills a military working dog would probably have, like observation, tracking, swimming, climbing, stealth, and UMA (or AMA since one could consider teeth to be a weapon) and voila!
Excavation = digging
Interrogation = intimidation of subject being interrogated by human handler
Scrounging = sniffing out foodstuffs, explosives, or contraband
Medical (Diagnosis) = I've read that some dogs have been trained to detect cancerous tumors.
A simpler solution would be for a handler's K9 companion to just lower difficult levels for their handlers' applicable skill checks (e.g. observation, tracking, scrounging, etc.).
The more I think about this, the more I want to play a character with a canine companion.