I agree, although I would like a Spy x Family NTR game the main problem is Loid, being a spy and an expert in deduction I think he would figure out the situation very quickly and it would lose some of the fun. I know some people prefer NTRs where the couple realizes the deception, but I personally enjoy it more when they don't find out anything.Spy x Family is one of the series I don't want to see a game made. The reason is Loid is supposed to be a high-experienced spy not a emotional teenager. So getting him to ignore the obvious signs of cheating is too much of suspension of disbelieve for me. A quick work for fap is fine but a game should not be so quick.
Anya is all about how much you enjoy lolicon. Desmond's a great cuckold for the NTR and Anya's own mind reading presents unique challenges for storytelling. If Anya was aged up to teenager I think there will be no problems.
And with Anya's involvement it's like you say, it's going to depend on how well each person accepts the lolicon, as half are going to want scenes with her and other people who don't.
I know Anya is also common among the Spy x Family NTR (a lot of times they put her in solo or with Yor), so she has to be a character that is used carefully. It could be something like the picture, that she as such does not participate or her character is not seen in the game, but through her we can see Yor's memories.