Rob - I'm a fair few thousand miles away from you, but here's some general purpose info to help get your research underway.
Now a lot of people associate Top Bar Hives with Horizontal Hives, and the Kenyan Top Bar Hive in particular - but this isn't the full story - as Top Bar Hives can be vertical, and Horizontal Hives can be framed.
Ok. A Horizontal Framed Hive - such as a Langstroth Long Hive - gives the same advantage regarding the lifting of combs one-at-a-time (rather than a box-full at a time), and yet it allows easy interchange with (say) the frames of neighbouring beekeepers if events should ever go pear-shaped. Assuming you use compatible frames, of course.
Then - rather than using a honey-bucket (and fighting off a cloud of angry bees), you could use a nuc box in your wheelbarrow instead. Fill that box one frame at a time - no honey is then exposed at the hive - and thus no clouds of bees. It's another possibility worth considering.
I'm getting on in years, and use both Horizontal and Vertical Framed Beehives - with each format having it's own advantages and disadvantages. With regard to the Vertical Hives, I'm adopting two strategies. The first is to convert my existing brood boxes to a deeper format. Now, although at first sight this may seem counter-intuitive - these boxes then become static (in the same way as a Long Hive is usually static) and no lifting whatsoever of that box is then required.
The second strategy is to convert to half-width those boxes which may require lifting from time to time, and simply use them in pairs. There are many ways of skinning the proverbial cat ...
BTW - you may want to re-think your pitched roof design. Generally speaking, although visually attractive, they're not very desirable. I have one ... only one.