Ability to assign better branding to a custom app solution for a client. Custom file icons, ability to change the application name from FileMaker Pro to whatever you want. Change the art on various warnings from a filemaker folder to art of developers choosing. Runtimes are more advanced in this way as the branding is a step better than what is available for a regular FM file.
Licensing page still showing FileMaker as the product and maybe a closing window like a runtime with FileMaker attribution.
Custom Apps generally mean Custom Branding to clients and this has been a topic of conversation with a few clients. Yes, the IT people will need to know about FM. The people paying for the licensing need to know about FM. However they do not see why the end users cannot be interfacing with something that looks like a true custom app with the company branding being more prominent.
FM iOS App SDK does this for FMGo, Web Direct is getting closer on this. I think client branding options for desktop FMP apps are important.