Where are the words "after this" in Amos 9:11-12? Oh I get it. When Amos says "In that day", it means "after this". Is that what you are saying.?
I hate to burst your hermeunitical bubble -- but those words of James -- they are Scripture. They are not just an interpretation of Scripture -- they are Scripture. And James is telling them that what Amos and the others prophesied regarding the restoration of the tabernacle of David could not take place until after God had first taken out a people for his name.
Any sixth grader with no preconceived theological notions, reading the words on the page can tell you exactly what they say and what they mean.
On the contrary, I think the sixth grader would see that James repeats Simon's point and then proves it with part of Scripture. He is saying the the words of the prophet agree with Simon. He is not talking about something that comes after Peter's point. Step back and read the verse without your preconceived theological notions.