The problem with the Tamiya German bikes (which, to be honest, aren't that much better than the bike in the picture) is that they're gentleman's bicycles, not ladies, and in the late 1930s/ early 1940s, well-brought-up ladies didn't ride such things. I don't see that the bike in the picture is too bad. You need to replace the spokes, but since the wheel rims are securely moulded to the front forks and the frame, this shouldn't be too hard, if you can lay your hands on some fine stainless steel wire. Time-consuming, maybe.
You can get etched bicycle wheels, but the problem with these is that they're for 27" bicycle wheels, while ladies bikes tend to have 26" wheels. It doesn't sound much, but it would throw the whole rim/ drop-out distances out. Other things that might need replacing include the brake rods (not cables on a non-racing/ cycletouring 1930s bike), but these can also be made esily from stretched sprue or plastic rod. It wasn't unusual to have lever brakes only on the front wheel. The rear wheel had a hub brake, applied by back-pedalling. I had one of these as a kid in Germany in the mid-1960s.
Don't add gears. North-Eastern France, away from the Vosges region, is pretty flat, and ordinary town bikes there, even today, tend not to have them.
Cheers,
Chris.
Cute and cuddly, boys, cute and cuddly!