Not sure how focused you are solely on wasps, but if you start looking at other invertebrates, there are actual animals that do engage in some sort of violent penis battle.
Many species of Pseudobiceros flatworms (particularily Pseudobiceros hancockanus) engage in "penis fighting". The flatworms have both male and female sex organs. They fight with their penises, and the loser gets stabbed through its skin and becomes impregnated. The winner gets to go off and have nothing more to do with the eggs/offspring. (There are many videos of this which show how dramatic and serious the fight is, the loser is often injured and clearly in bad shape compared to the winner.)
Bed bugs (Cimex sp.) breed through "traumatic insertion". The male stabs the female with his hypodermic genitalia and deposits sperm. The sperm travel's through the female's body cavity into sperm receptacles and eventually into the female's ovaries.
Male Dana octopus squid (Taningia danae) use their sharp beak and hooks to cut large (5cm+) gashes in the females of the species. They then use a penis-like tentacle to deposit sperm packets directly into the cuts.
The sea slug Chromodoris reticulata can regrow its penis. After mating, their penis breaks off and remains stuck in their partner. This help ensure that its mating is successful, and somewhat limits competitors from mating with the same sea slug. Having a broken off penis isn't bad for the sea slug, since it was only using 1/3 of it. The rest was coiled up inside its body. Once the exposed 1/3 breaks off, the next section uncoils and is ready to use (this takes about a day). After that breaks off, the final section uncoils. If all three segments are used up the sea slug can even completely regrow the whole thing (although this takes a long time).
These are just a few example. There are many other weird examples from animals, especially creatures such as: slugs, snails, insects, flatworms, sea slugs, octopus, and squid (if you're looking for species to research). Given how often something like this shows up in animals living on Earth, some sort of penis type weapon developing on an alien seems plausible, but it does all depending on how you phrase and explain it.