I would think that the diplomat dog would be probably pretty busy with the Dogs' own business. And what would we be expecting out of one? As far as I recall, the lack of skytowers and seals mean that the Pangolins have stopped advancing and, at worst, are consolidating if not outright retreating to make their advances holdable.
This isn't widely known to the Dogs for the same reason the Dogs haven't ever seen a Pangolin - the 7P information network is not great. And arguably, we're the ones that are going to need to forge relationships due to our 7P trade network idea.
In sum, I'd say that we include our trade network idea and desire to therefore have neutral relations between all Leaf summon clans at the moment. To be honest, that sounds like something that Cannai (or at least his diplomatic corp, such that it exists) would want direct input on, and we shouldn't necessarily ask for one.
Personally,
[x] (Doggo) A combat dog
[x] (Doggo) A tracking dog
[x] (Doggo) A ninjutsu-spec dog (element humans don't have)
Both are very important - I'd say that with a combat dog we should consider coming up with something that distinguishes our request from what Candoru already gives us. I doubt we're going to get a jonin-powered dog off the bat, so we should zone in on a specialist - maybe ninjutsu dog? Generally Uplift is less long-ranged, so that would certainly be helpful.