I know it must be hard to work in a game and invest into it just to have some guy telling you are doing things wrong. It must really suck, I know, you must hate me, but trust me when I say that my intentions are not bad. I think it's better to have an opinion of someone that disagree and can give you another point of view, rather than just having everyone say "your are doing great", just to finish your game and find out that is not as successful as you thought it will be. So yeah, I'm that guy, and I'm not saying that I'm right, but I want to give you my impressions in hope they are useful to you.
I think you are doing things backwards. I mean, if you have to choose between futanari fans and NTR fans, it will be much more profitable to choose NTR fans, simply because there are a lot more demand for it as show
IN HERE (futanari is in the 12th place by the way). Also NTR is one of the most polarized fetishes ever, most people either love it or hate it. So,
you will find a lot more fans of NTR than don't mind futanari, than fans of futanari that don't mind NTR. I think it will be much more effective doing it that way. Trying to please everyone, or most exactly, not trying to displease some fans, is in my opinion a formula for dissaster, and you can check quite a few examples of that in this thread. Don't making it Mystery because you don't like it, it's a totally valid reason that I can respect. I mean, there is no point in making something you don't like. But trying to water down the NTR feeling just to please some fans is another matter all toguether, after all you do like NTR don't you? And NTR well made I assume.
On the other hand, assuming that the lack of futanari NTR games is proof that not many people like that kind of stuff is another big mistake. Before
Greater Heal and
Sei Yariman Gakuen Enkou Nikki came out, there were pretty much no games with the JK prostitution bitch theme. Now that's a very popular fetish, to the point that there is even
a developer specialized in making those kind of games. No fetish or trent is popular until someone developes a good game/manga/CG/etc. and makes it popular. I'm sure there will be a lot of demand for futanari NTR if someone make a good game about it. It's kind of contradictory that you expect it to sell while thinking that not many people like it (Then why don't just choose something more standard that sells?) I think the idea of futanari-NTR is great, as long as is well made. If you want to make a futanari NTR game, then make a good futanari NTR game, with strong NTR feelings and a horny futanari. That way, both futanari and NTR fans, will be pleased. If you make something in between just because you are afraid some people won't like it, then better do a vainilla game, or you will probably end up dissapointing NTR fans (and there are a lot of them, for some reason this thread is the second most viewed in the whole forum). One comment from a dissapointed fan could sink your ship, so you are risking a lot by making something NTR but not quite (I think you could crash and burn making it that way).
On regards of the gameplay I think you are doing it backwards as well. Think about it. Why do people play this kind of games? Is it because of the gameplay or because they want to fap to the story? It's obvious the later. So into developing a game, the gameplay has to serve the story and not the other way around. So if the gameplay requires the husband to go away, watering down the NTR feeling along with it, I'll rather change the gameplay. And if you want to maintain the gameplay at any cost, there are ways to go around it, withouth the need for the husband going away. For instance: Why not make the futanari a neighboor? That way she can be close to he wife when the husband is working. Or make the two girls come to the house earlier, while the husband is still at work. If the husband comes later, they can have an hour or two alone. Doing it like this also allows you to have some juicy "almost caught" moments, that are really good in NTR. That also allows you to have some "stealth" scenes earlier in the game (and I can imagine a few that will almost only work with futanari and that I would love to see). You can also make the wife a housewife, so the futanari can monopolize her while the husband is at work. I think you should be flexible with your story in order to give the stronger erotic (and NTR) feeling posible. So, at least there is a strong reason for the wife and the futanari being coworkers, then there is no reason to change the setting a bit (they can fuck around in the workplace too). Of course this is all assuming you decide that sending the husband away is a big mistake. I think it is, for all the wasted potential: the "netori guy" is a futanari, she will go under the radar withouth the need for the husband to go away. Sending the husband away is like throwing to the trash one of the main reasons this game will make a good NTR!
Sory if I'm harsh but, I have always thought that futanari in NTR will be a blast for all the potential it has. Also futanaris tend to be really possessive and agresive, so they make a great character to steal the wife/girlfriend. I always wanted a developer to make a good futanari-NTR game. I also wish some developers will read this thread and realize what we NTR lovers like and what they make that we don't like. So watching someone in this thread develope a futanari-NTR game, while wasting a lot of its potential, making the same mistakes we all complain about in here, just drive me nuts! But well, in the end, it's your game. I can only tell you what I think based on my experience watching/playing/reading NTR manga/VN/CG/etc. and what I have read and contribute in this thread.
I'm sorry for the long post and being kind of rude myself. I wish you the best luck with your game! I really do!