Actually, I also a bit lean to a porn viewer side. For me, I priority sex contents maybe called fapability? may be the most for this kind of game. But both of you said were true If you focus only throw in porn it's porn viewer and it's surely boring.I played many html porn that served just like porn viewer and I got bored of it quickly. If you too focus just on the mechanics or overdone it. It will be too complex and tired to play. Right now, I think you're still good in both side hope you can keep this for long.
I have a good example on this, perhaps you know Dungeon lord V. 1.0, a good html game on this site (Like Yours) my favourite ! because the storyline is good and the most important is it very easy to play and have very good continuity on sex contents and fapability at the same time! (It's even have 1 hand mode that made you can just spam spacebar through the story for a while on purpose hehe) After such good feedback mix with comments+polls to make it more grand, complex and focus on continuity of story line. The author come back with new version Dungeon Lord:a New Beginning with quite more complex mechanics and abandoned real porn to rely only 2d 3d anime things mainly because porn gif doesn't match the story,Like you cannot find real elf person costume porn to use with elf screen haha. (This is bad for me since it got more complex and also lost it good real porn Gif of previous ver.) Shortly after, the game got abandoned. Sad but just wanna told it. Didn't blame the author at all. Devs have the right to do whatever on their game even abandoned it.
Summary >> Simply just try to keep the balance will do it. May be challenging but I think you're still on the right way now.
My personal thought in prevent complexity is maybe should just not put too much command in same page or with too many layer to choose/click to perform a thing in every turn,Imagine in some games have to choose position out of 10 position afterthat have to chose sex command over 20 sex command every times. (like Liliththrone or Nightgame by Silverbard 20+ button with 3+ action layers every fight/turns ouch...) And avoid being force to repeat command too many times. For Example,Now If I wanna got climaxed and my max stimulation is 50 I need to masturbate around 10 pts 5 times to get 1 climax, during that time I may died or enemies already died. So, to fix it I should just raise the masturbate value more to scale with stim so just do it about 2-3 times, I got climaxed. Problem solved EZ!