You don't need to go for something as complex as a SA hub.
It's a bike not a trike, so you're not going to balance it with a first gear much below 20".
If you don't intend to pedal downhill fast then a top gear of around 100"-120" is fine, The slower our natural cadence then the more towards the top of this range I'd go.
This gives you roughly a 6x range which is easy to do with a MTB triple and a wide cassette.
The backs easy.
I think the best wide 9 speed cassette is the 12-36 one as all the steps between the gear are fairly even. This makes the effort needed to go from one gear to the next very predictable.
The only downside is you may need to use something like a Roadlink/Goatlink mech extender to use the 36t sprocket.
The fronts a bit more tricky.
Find your BCD and use this page ->
https://www.sheldonbrown.com/cribsheet-bcd.html to find the minimum size of chainring that will fit you spider.
Ideal would be something like of 50-38-26.
If you want to workout the minimum inner chainring then the chain drops by 2mm per tooth reduction.
Put the chain on the small chainring and measure the gap between it and the bottom of the cage.
In theory you can use an 11-42 cassette with a sub-compact double.
But it gives no greater range than the above setup.
Plus I think the best 11-42 cassette is the SRAM 11 speed.
So more hassle than it's worth.
Luck .............