I've been looking at the Larkspur as a possible ride for my wife for the same reasons (and because it comes in a small enough size for her): wide 650b tire clearance, steel, step-through, 1x11 with 38t chainring by 11-51t cassette (or 1x10 on the Larkspur 1 with the same 38x11-51t), even comes with nice enough tires. Could take or leave disc brakes but the Shimano deore hydraulics are good (the Larkspur 1 with Tektro low end hydraulics are ... fine, not great). These have been hard to find in stock (and impossible to find used, likely a good sign). Unfortunately, between 2020 and 2022 the price has jumped substantially (the Larkspur 2 was $929 back then, $1,199 now without changes to justify the cost increase, appears to be related to supply and demand). That took it from a great value to a good value in my book.
We ended up getting a Kona Coco which is similar to the Larkspur 1 but in aluminum (and significantly lower price, used [very little from what I can tell] on craigslist for $500). When our kiddos are a little older and we can go on longer rides together then I'll be looking for a used Clem L or Larkspur. In the mean time the wide tires and lower pressure are making up the difference for a comfy ride.
That said, I like your 'find a used mixte and build it up as a poor person's riv' idea ... perhaps mostly because I'm currently in that same project with a Nishiki Bel Air ;-) This will be for my dad who, after 80 years, prefers a lower step through/over.
Notice that THREE pulley rear derailer!
Notice that THREE pulley rear derailer! Sugino VP triple crank, clearance for
maybe 2" wide 26" tires, MKS pedals, a nice setback seatpost hidden by being lowered all the way here, color matched stem, power ratchet Suntour friction shifters (not exactly but similar to the Silver shifter precursor), and nice Dia Compe brakes/levers. Steel and lugs and such. Happy with this find that seems to have spent 20 years resting in a basement. Already cleaned everything and removed some rust pitting, new cables/housing, trued the wheels (tension meter at 22 on the front, rear is 25 drive side and 17 non-drive side), a lubed/greased parts as I find them. Stem's original red grease was still in great condition, brake pads were barely worn so I think it's got very few miles ... so far.
Good luck on your search, the Larkspur will be great but the used restomod is another fun option ... do both!
Abe