I'm workshopping a sapient fantasy species, that, in lore, was designed by external forces to be a biological weapon. This species accomplishes this with a form of sexual parasitism that enables them to outcross with several other unrelated sapient species, while still propagating their own; i.e: an alien interbreeds with a human, but the offspring is a member of the alien's species only, rather than a true hybrid.
The problems I'm encountering are my own hang ups of making this still a dual sex system, as well as mental roadblocks with figuring out if this is a sustainable system or if the species would die off in a few generations (or less). I also do not want the offspring to be genetic clones of the parasitic parent, and, ideally, I would want them to incorporate at least some of the genes from the other parent, even if those genes are only responsible for superficial characteristics like eye color. I also want this set up where two opposite sex members of the same parasitic species can sexually reproduce with each other and create offspring with an even 50/50 combination of their genes.
My questions specifically are:
Can this system exist while still retaining a dual sex system (male/female) where both sexes gametes overpower the gametes of their mate? Something similar has already been established for female 'aliens' in fantasy, such as the Asari from Mass Effect, but how would males be able to accomplish this? One concern is fetal rejection and gestation times in other species, and how they would be able to 'force' the 'incubator' (for lack of better words) to carry their young.
Does this system exist in nature? From searching, I was brought to a lot of different terms, from Hybridogenesis to Kleptons, etc, but with my limited understanding of biology, nothing seemed to fit, but it's possible the jargon was just lost on me.
Is this system sustainable, or will it collapse from inevitable genetic bottlenecking or other structural weaknesses?
I have considered alternative solutions to this system, and I am okay with making some concessions as well. One such consideration was the parasitism being more similar to sacculina barnacles and their relationship with crabs (where they effectively castrate their host and substitute it with their own reproductive organs), but I'm not sure how this would scale up on a sapient species that otherwise reproduces sexually. I also considered having one sex be haploid, and one sex be diploid, or potentially just hybrids being haploid and 'pure' offspring being diploid, but I don't know what this would entail for any future generations. If it comes down to it, I am okay if the male/female sex distinction is purely superficial, and both 'sexes' on technicality have ovum and testes (albeit less developed or more developed depending on 'sex'), but I want to avoid the temptation for this species to just propagate via cloning. I do want the species to utilize some level of recombination for all of it's offspring.
Some details about the rules of the world:
There is magic, though the magic is alchemical, and at a basic level, only capable of transmuting elements. Additional confines to this magic are that atomically similar elements transmute cleaner and consume less magic than transmuting elements on very different sides of the atomic table. Larger structures can be altered, like complex molecules and compounds, though they consume a proportionately larger amount of magic than just altering a single atom. Nonetheless, this magic system, in it's handwavium, cleanly absorbs any kind of radioactive decay that would ordinarily be produced.
The sexually parasitic species gives live birth, is warm blooded, has a placenta, and their young are precocial and do not need to breastfeed. Every sapient species they can reproduce with is also warm blooded and gives live birth. The parasitic species does not need to be able to reproduce with everything like a xenomorph would, just other warm blooded species that give live birth.
If more clarification is needed, please let me know! As I said before, my understanding of this facet of biology is very limited, and it's very possible I'm missing a few key details or completely misunderstanding certain concepts. I appreciate the help and consideration!