They've tried this before in the 1990s, it didn't work well. There are many variables, and a huge variable is: your vendor's modules/software doesn't do what it says it does. Keep in mind that marketing people, not software engineers, usually write the marketing material. Thus the marketing people really don't understand what a product does, and when programming gets involved, details matter. This was so bad that in one company I demanded to review all documentation written for changes I made. (We had a marketing person writing technical documentation. Sometimes it lacked important details, and sometimes it was just incorrect.)

Example: In the 1990s I was using MS Access. The box said it was backwards compatible with all versions. It was not. It only converted forms, queries, reports, and macros, not code. When a new version of Access was installed, all code had to be retested, and sometimes rewritten. If you used a lot of code, it was a sure bet something was going to break, especially if you used a DLL that got upgraded. When the OS or another product (like Access) was upgraded, some DLLs had their data type changed to another larger type, from integer to long for example.

My point: you really don't know if your vendor's software will do everything it says because you can't trust what's on the box or in the documentation. Good luck getting your vendor to fix something (that should have been designed correctly in the first place) just for you without paying through the nose.