WHAT WE KNOW: Velorek was first introduced in The Way We Weren't, through Aeryn's flashbacks. Aeryn's last line about Velorek's fate is, "They never got him to talk." Crais's plan was to impregnate a Leviathan and breed a PK-Leviathan gunship. Velorek knew about the plan, and stopped it by installing the conception shield (heretofore known as CS). D'Argo, way back in They've Got A Secret, shattered that shield and indirectly impregnated Moya. Talyn was born due to that. Therefore we KNOW that the writers had enough forsight to anticipate a TWWW sometime in the future when they wrote TGAS.
(for more information regarding the theory, COULD VELOREK STILL BE ALIVE?, or: "Evidence collected throughout various information deposits points out the fact that there is a bit of a chance that Velorek might still be alive", which is at http://www.fortunecity.com/business/ziff/286/farscape/number-six-a.html)
WHAT I SPECULATE: Mr. Gunshock is a relative of Velorek's. Possibly even Velorek in disguise. Velorek already displayed a talent for untranslatable languages evident several times in TWWW when he actually conversed with Pilot in Pilot-speak. Mr. Gunshock was also very good with languages, able to converse multiple times with the Diagnosan.
Also, regarding the Diagnosan: I think two things regarding the inability to translate his speak. 1) The Diagnosan was using obscure medical terms which, like "frell" or "dren," could not be handled by the translator microbes. 2) The Diagnosan of Pilot's species, and he was speaking Pilot-speak. This theory adds weight to the greater Velorek idea, but it is flawed. First of all, we've seen Pilot, and Pilot doesn't look like Dr. D. However, we only had a brief glimpse of Pilot's home planet, perhaps he was one of a type of Pilot, or a mutant or something. And I have just come up with a third, way-off-kilter scenario. 3) Dr. D. is NAMTAR! Or at least a relative of NamTar's. Or possibly someone who NamTar did experiments on. How else do you explain that schnozz of his?