Could you add a lower height option for the custom girls? currently the lowest is 4' 11". if that could be lowered to 4' 0" it would be great.
Also, maybe you could add more weight stages. like between the current stages, so the progression could go something like this: anorexic > thin> pudgy > slightly soft > soft > chubby > plush > husky > thick > hefty > wide > fat > bbw > chunky > very fat > round> rounder > ssbbw > pillowy > severly fat> ballooned > barely mobile > almost immobile > blimp > immobile > bed-bound > enormous > bed-filler > mountainous > blob > room-filler
Another location I would recommend adding is a beach to swim at, maybe that gets unlocked after visiting the shops to get a swimsuit in whatever size the woman is at. If she goes up a couple sizes without buying a new swimsuit, the location is locked until a new one is bought.
And an idea for traveling once the woman gets too fat to fit in a train, would be the option of using the canal. England has an extensive canal network, built to link towns before trains became a big deal.