有可能，但我不确定性能如何。
其基本思想是：

• 将字符串拆分为整数和小数部分
• 将每个部分转换为数字：

o迭代每个部分中的字符
o将累计值乘以10
o添加当前数字的值

• 将小数部分除以10^（位数）
• 将整数部分和小数部分相加得到最后的double
• 删除临时字段

db.collection.aggregate([
  {$addFields: {
      split: {$split: ["$value", "."]}
  }},
  {$addFields: {
      whole: {"$arrayElemAt": ["$split", 0]},
      fraction: {"$arrayElemAt": ["$split", 1]},
  }},
  {$addFields: {
      whole: {$reduce: {
          input: {$range: [0,{$strLenCP: "$whole"}]},
          initialValue: 0,
          in: {
            $add: [
              {$multiply: ["$$value",10]},
              {"$indexOfArray": [
                    ["0","1","2","3","4","5","6","7","8","9"],
                    {$substr: ["$whole","$$this",1]}
              ]}
            ]
          }
      }},
      fractionVal: {
        $reduce: {
          input: {$range: [0,{$strLenCP: "$fraction"}]},
          initialValue: 0,
          in: {
            $add: [
              {$multiply: ["$$value", 10]},
              {"$indexOfArray": [
                  ["0","1","2","3","4","5","6","7","8","9"],
                  {$substr: ["$fraction","$$this",1]}
              ]}
            ]
          }
        }
      }
  }},
  {$addFields: {
      double: {$add: [
          "$whole",
          {$divide: ["$fractionVal",{"$pow": [10,{$strLenCP: "$fraction"}]}]}
      ]}
  }},
  {$project: {
      fraction: 0,
      fractionVal: 0,
      whole: 0,
      split: 0
  }}
])

Playground