MC is not going to be your typical "loser" in NTR games (pencil-dick, spineless, etc...), but I can see why you would think that. The state of NTR games is... not looking good. Which is why we are doing what we're doing.
Your approach to implementing NTR reminds me of Elf، This reminder
made me want to talk about his core principles regarding NTR games
I’m not sure if you know Elf or not—he stopped game development about 10 years ago. Many consider him a legend in the realm of Netorare
He paid meticulous attention to the
depth of the MC and FMC's relationship and
their personalities. Back then, when another man attempted to Deceiving/ Creating big problems for the FMC,
it created an intense mix of sweet excitement, stress, and tension for the player
Unavoidable NTR can be excellent, provided that the MC, with the player’s guidance through "choices" manages to maintain an emotional and sexual relationship with the FMC. This means that while sexual encounters between the FMC and the others occur, the MC and FMC remain in a romantic relationship. If they were to become emotionally or sexually detached or lose the love between them, NTR wouldn’t deliver that same thrilling satisfaction as before, the only thing that remains is a feeling of despair
I hope "choices" in this context capture that crucial aspect effectively
This means that the MC (who, as you mentioned, isn’t a loser) can, in one of the two paths, by "choices" to maintain a deep romantic relationship and their personalities while also witnessing the FMC’s intense sexual encounters with other men
for logically justifiable reasons