As you correctly state, in the UK most kitchens are based around a 150mm legs/plinth, 720 cabinet and a 40mm worktop making 910mm, there may be a few variations of this, ie howdens have a 160 ish plinth, b+q have taller cabinets for their true handleless at 754mm plus plinth making 942mm including 40mm worktop.

I've in the past when a customer has requested taller worktop height, i've offered 200mm tall legs and plinth and kept standard sized base units at 720mm, but this also keeps the costs down. The other way to add height is to alter the worktop height, with wood worktops a half decent fitter could increase the worktop thickness easily by sandwiching strips underneath so you could have a prep area of raised worktop, for granite and quartz its quite easy to make it look much thicker in fabrication (except for curves)

But looking at german kitchens, I sometimes copy Nobilia cabinet sizes, they have XL base cabinet sizes at 792mm tall and then they offer plinth heights of 70, 100, 150 and 200mm, they don't though add extra drawers, but just change the size of the facia's, so in theory you could have a 992 tall unit with a 40mm worktop. I should imagine other german kitchens offer the same. But if you were to contact a local independant supplier or you can direct message me, i can design a kitchen to suit your requirements. The limitations though are the doors available and how much a designer can think outside the box. Many of the doors i use are available in made to measure sizes so i can get my cabinets made to suit and its not as expensive as it sounds.

With regards to selling the property afterwards, i go into a lot of kitchens to survey and when i say to clients your kitchen units are high or low they really don't realise, i then explain and show them how a 'standard' kitchen would be and give them the option of keeping the height they're used to, explain how it would look and the options to get it or changing to a 'standard' height. So when it comes to selling i don't think most people would notice within reason and since the 60's i believe average heights have increased so it may be the kitchen industry thats not keeping up.

My in laws have a ‘tall’ kitchen. They raised the units up 6 inches and had double plinth. They love it, as an average height person I find it really difficult to use. The other thing to note is that it’s a galley kitchen and the tall units make it feel narrowerer.

I'm a shortie and so selected a Schueller/ Schuller kitchen (german brand) as they have small, medium and tall base units.

You can fit standard kitchen cabinets on a taller base frame or buy taller adjustable legs for the units to sit on. Either way you’ll need to make some custom plinths (plywood/MDF?) and colour match doors.

The extra void would be a good space to install a plinth drawer.