Yeah, Aya/Harry's characters are in a bit of a hole if we want the same type of NTR to work. One viable route HC could take is voluntary NTR on the part of Aya/Harry (or Netorase).
Aya has a strong personality, but both Laura and Harry have very weak personalities. This is what Luca would exploit. (Also clarification before my example, haven't played .1 of new Aya update, and been awhile since I've started just gallery skimming Laura updates.)
Rough example scenario:
(Aya/Harry are now together, and Harry broke up w/ Laura. Luca takes initiative to 'repair' relationship with Harry, while trying to look for weaknesses.)
- Harry starts receiving various explicit videos. Starts w/ regular porn, then over time shifts into bull/cuck porn.
- Luca mentions receiving the same videos in the office, tries to convince him to keep watching. At the same time, Luca tells Aya that Harry may have 'fetishes' that he won't reveal to her.
- If Harry continues watching Aya catches him, plants a seed of doubt.
- She talks about it with Luca, and Luca tells her they can continue testing him. Maybe give him a gift to show that she doesn't mind. Aya shuts him down, saying she won't do anything with him. Luca backpedals, saying they can use a substitute, ease him into it, and suggests using Laura.
- Luca seduces Laura, and records videos for Harry using her, but w/ Aya involved (maybe over the phone at the start, then in person later.) Aya sees that Harry is watching/jacking off to the videos, so she continues.
- Dress up Laura as Aya, do more explicit 'pretend NTR video'.
- They take a break. Maybe choice here could be Harry stops cold turkey, or picks back up jerking off to NTR vids.
- Aya catches him again. Convinced that this is what he wants, SHE decides to work w/ Luca again to record gift for their anniversary (or some other holiday).
- Balls in Luca's court now and he wants to escalate between him and her, leaving Laura out of it.
- Eventually continue into real sexual contact between Luca/Aya based on how Harry messes up/any exploits Luca finds over time.
- As Harry continues watching videos, starts getting suspicious. (Whether he acts on his suspicions could lead to different endings.)
Obviously, this scenario wouldn't be perfect and I'm probably forgetting some plot details that would leave gaping plot holes, but I do think following the same path where Aya is treated as weak as Laura will lead to some very unsatisfying paths.