Good guide. I'm sure it'll help a lot of people. I believe that オーダーメイド is the more accurate antonym of 既製.

I wasn't familiar with the term パターンオーダー, but the following site gives an explanation. It says there are three types of オーダーメイド (the other two being フルオーダー and イージーオーダー). They say that パターンオーダー involves the tailor selecting the best fit from a number of sample patterns, and making minor changes if there are any parts that aren't a good match. At the other end of the spectrum is フルオーダー, which is making a tailored suit based on your measurements and not a pattern. So it's not wrong, but パターンメイド is a specific type of tailored suit.

https://fabric-tokyo.com/answer/suit/pattern-order-suit#1-2-%E3%83%91%E3%82%BF%E3%83%BC%E3%83%B3%E3%82%AA%E3%83%BC%E3%83%80%E3%83%BC%EF%BC%88%E5%88%9D%E7%B4%9A%E8%80%85%E5%90%91%E3%81%91%EF%BC%89