But what good would that do.还是But what good that would do.

应该是后面一句：But what good that would do 意为：但是那将会带来什么好处呢.因为你后面用的是句号,应该用陈述语序.
如果是问号就为第一句But what good would that do?
因为what这个疑问词作的是后面的宾语,do what
具体分析如下：
特殊疑问句有两种语序：
1．如疑问词作主语或主语的定语,即对主语或主语的定语提问,其语序是陈述句的语序：
Who is singing in the room﹖
whose bike is broken﹖
2．如疑问词作其他成分,即对其他成分提问,其语序是：特殊疑问词+一般疑问句【特殊疑问词+be/助动词/情态动词+主语+谓语What does she like?What class are you in﹖Where are you from﹖
What time does he get up every morning﹖
How do you know﹖
- -!其实口语中两者都可以的 我也被弄混淆了