I really prefer the hydraulic discs too. One of the hills in my way to work is very steep, and I can ride down it much more confidently on the mountain bike, especially when its wet.
On the other hand, the more I think about it, the more I like the idea of going back to basics. I keep threatening to do a bike maintenance course, but the course near to where I live doesn't cover hydraulic discs, shock absorbers etc. Having a simpler bike would mean I could do more myself.
I too have a hardtail mountain bike, they are versatile, they can ride off road, they can tour, this is where the low gearing helps for me and my OH too. I even did a century ride on mine. They would not make good road racers though!
Do you ride the mountain bike offroad? If not maybe the Dutch type bike is what you are looking for.
I also like the "Dutch" type bike after a visit to the Netherlands last year.
I now have a a Pashley Paramount with North Road bars and the ding dong bell, very popular with the pedestrians and always gets a smile!
I do regular 30 + miles rides ok, but if I want to do big hills it is not really ideal as the 5 speed hub gearing is too high for me and the drum brakes although good in the wet are not as good as a disc for coming down big hills.
They do a version called the Penny for women. http://www.pashley.co.uk/products/penny.html
For a true Step through/Dutch type bike with MTB low gears for a hub drive you are probably looking at a Rohloff or have the gearing changed to MTB gearing for derailleurs.
To have the disc brakes also?
In the Netherlands you don't need any more than the Sturmey 3 speed hub, 1st and 2nd are for the windy days or "Dutch hills". Consequently they do not have the need for disc brakes, I didn't see any bikes with them while there. Someone like KTM must do them for the European trekking bike market where hills are expected.