@nsantalu Good read. Thanks for posting all of the steps and links, as it helps others see first hand exactly what you are building.
The evolution you describe seems to be common among DIY arcade builders over the past decade or so (pre-raspberry pi). While plenty of users buy the X-Arcade solutions and stop there, it can be a gateway to other considerations leading to more controls, more customization, and generally, a much deeper understanding of the hardware and software. I too am curious about your answer to @chigundo's question: knowing what you do now, if you were going to do it over again, would you follow the same path or go completely scratch built?
The one fly in the ointment of an X-Arcade story is the image which they provide for download as the suggested start. By downloading their image and continuing your build from there, customers are in an unsupportable situation--we have no idea what configuration changes X-Arcade may have made to the image they are providing. Moreover, they are in violation of several license agreements which is a legal problem. Finally, the recommendation against full updates is sure to eventually cause support issues. This is unfortunate because it is not difficult to start with the official RetroPie image and install the relevant drivers after that.
The silver lining is that, if necessary, X-Arcade owners can switch to an official RetroPie image at any time and they have a decent bundle of arcade controls that are likely going to last a long time.
I am anxious to find out what you think of the TurboTwist 2 spinner. I have two of them in my cabinet.