This may be totally not what
@BurroBabe wants to hear, but her needs and requirements are far enough outside of the norm that manufacturers cater to that I would pick a bicycle she likes that does what she wants, and convert it to an ebike. Bearing in mind that the weight requirement is likely to still go out the window thanks to the need for range, which in turn will crank up the weight.
My daily driver's battery weighs more than my entire road bike, which with its magnesium-alloy 59cm frame weighs in just a hair under 20 lbs.
View attachment 175833
Not saying you have to go so big on the battery just making an amusing (to me at least) observation.
I'm going to have to admit I didn't pore over the entire saga of this thread. Hopefully I've skimmed it closely enough to not commit too many mortal sins in the following recommendation. Maybe there's somewhere to go here with a conversion, because for a manufactured ebike... you can forget it I think. A conversion is going to get you VERY close to your desired result out of the gate with the motor and battery coming in after the fact very nicely if you do the bike right.
So starting off, it seems what is desired is a gravel bike that can do duty as a touring bike, with panniers. Since a suspension fork is desired, I'll write off the front rack and panniers (which served me very well I might add before I went to dedicated cargo builds, but lets walk before we fly). Next we need something that is very nearly unheard of in the ebike world: A frame sized for the smaller rider. This will get us out of the 20" wheel size, ideally.
Surly bikes are built with really strong chromoly frames, and quality components. I have a BBSHD-powered Big Fat Dummy which I use for bikepacking, but thats obviously an insane choice not on the menu here. What Surly DOES have that is smack in the ballpark is the Grappler.
Grappler is the drop bar mountain bike and bikepacking bike purpose built for loading up and hitting the most agressive bikepacking trails.
surlybikes.com
A dedicated drop-bar trail bike with 27.5" wheels and 2.5" tires. And a frame that is sized down to XS which is suited to riders whose height starts ad about 4'7". The size SM is rated for 5'0". Standover is 2.2 to 2.5 feet. So we've come up with a bike that actually fits the rider (something ebike manufacturers as a general rule don't do) and have thus bypassed the circus-clown-bike wheel size. Check the frame geometry for stuff like reach, but for my money, you should always expect to change stem length and maybe even swap the seatpost to deal with a different (or zero) setback.
The Grappler uses the inexpensive Microshift Advent X drivetrain, which is extremely reliable and has an 11-48T hardened steel rear cluster, which will be really important when it comes to working in the motor. I use Advent X on my own Bullitt hill climbing cargo bike where I am dealing with 500 lbs of total system weight and hills as steep as 16%. So if it can handle that and shift smoothly it sure can handle this lighter duty. The frame has M5 bosses upper and lower so you can mount a serious rack on it (an Axiom Streamliner rated for 50 kg would be my choice), and do panniers of any sort without issue. The front fork is a standard Surly with barnacles everywhere so you can also mount a front rack (I use a Blackburn Outpost on Surly forks), but I expect that fork is going to be expendable in favor of a suspension fork, sadly. The WTB rims used have a 40mm internal width which will let you easily handle a 3.0" tire (the bike comes with 2.5's which might be plenty for you).
For something a little closer to a road-tourer (and a little less happy with washboard) there's the Surly Disc Trucker. For a flat bar version of the Grappler, there's the Bridge Club, although neither of those have drivetrains I would trust with the next step: Adding a mid drive motor.
Again assuming the Grappler is the choice, my personal pick would be a Bafang BBSHD, which you would then adjust to turn it into an ideal cyclists' configuration. I wrote that up here and using all of the settings I list in that article, you would adjust the one setting noted in that article to ramp the overall pedal assist output up or down. My minimum setting feeds a maximum of about 450w peak to the motor so its quite tame, which in turn extends range by quite a bit. I suspect you would pick something in the middle, or go all out and just use the lower PAS levels, which is what I do in hills.
Explore enhanced BBSHD programming for pedal assist settings that don't let the bike run away from you, and throttle settings gentle on the drivetrain.
talesontwowheels.com
You could also skimp a little and use a BBS02, which is cheaper and less robust. For a bike I want to depend on, I would always choose the BBSHD. Its a trooper and you can't break it. Not so with a BBS02 which can be fried if you beat on it too hard (which you are very unlikely to do but still...). Dialed back the BBSHD will be operating at 20-50% of its capacity which just means it will never stress itself and last forever.
Since these bikes all have triangles without shocks in them - and they are actual triangles - I would pick the battery from USA-manufacturer Bicycle Motor Works after I have acquired the frame and know the dimensions. An in-triangle battery bag would hold it (do NOT put it on the back rack). Triangle size on an XS frame may make it a lot smarter to pick a Small size instead, or even a step up from that to Medium if you can get away with it. Check the frame geometry charts to see about that.
As for a suspension fork... well like I said before I would personally go for a suspension stem from Kinekt first, and keep the fork as-is at least to start. But the axle-to-crown on the Grappler is 420mm. Surly says thats the max height for a suspension fork, but I think you can fudge that a little. I'll leave fork choice to you.
If you don't convert a proper, quality bike yourself I think the list of compromises and things you find undesirable will be a lot longer.
The first day of assembly is laid out here item by item. By end of day we’ll have a roller we can sit on and push around, not a box of parts we have to carry.
talesontwowheels.com
easier than hauling on a bike on the hills and through brush on the farm.
