Yeah, I think it's a great addition!
I'm neutral, I guess.
I have this specific opinion... (specify in post)
well you r right about parental or govermental control issues regarding the export of the mangas that might deemed unfit for children until the internet(thou even before that; ppl when they want something they usually get it regardless of anything. i know i did.) and about the need for a in-depth research about the explict material issue; i cant give you definitive answers or publicaitons(well i found them but i neither have time nor the inclanation to pay for an article that will have little benefit since i am neither a manga historian nor a critic) and the only research i did was a quick wiki 1. also u r right about these sub-genres being longer in japan then we may realize considering 800 years of history of manga. i can only give you relative numbers based on mangaupdates which isnt exactly absolute. but my point came from the censorship japan had on publishing these subjects for younger audience till the late 1980s.(which with increasing numbers of enjou kosai and such another bill passed in 2010) after the relaxation of censorship more and more such subjects started to grow from shounen demo(as u have mentioned with dragonball) and jumping to other demos.
The only Adult content I think woudl work is if it is warranted in a romance scene. Skip all fan service, leave it to the Shonen based stories. I am of the upper age end of the Josei community, and just the right amount to hint is all is needed.
but maybe fan service in the shoujo/josei magazines are different. Like a shower scene, or something. I dunno how that would really work but in RL that works pretty fine as a fan service directed to the female viewers lol.
It depends if it the smut fits the story or not.
If it's out of place, not quite enjoyable and abrupt. a "Wait? What?" situation.
If the flow of the story is good, I'd feel OK with smut.
But yeah, it does add to the realism. Like necessarily but not going to far.
I'm mostly neutral about it in Josei but in Shoujo, I might be a little uncomfortable but still depends on what I mentioned above.
It just depends tbh. Most josei titles have smut in them, since I mean it's targeted for the older women out there. I avoid josei when I'm not in the mood for smut and vice versa for shoujo if I want some smut. Sometimes I like having the smut but all in all, it just really depends on how the smut fits in to the story. Most manga nowadays just slap some smut on there just because that's the trend. I mean, that's the reason I'm reading the manga in the first place, for the story. If I wanted some smut, I could just play some R-18+ visual novel or read some hentai/ecchi (some of which have really good stories imo).