Ask HN: Large gov project ahead. Howto avoid the CMS Trap?

Hey HN, 😉 I've two large projects ahead and in one of them I am assigned to a project manager (big co. guy). However in the first conference, the word Joomla made it's first appearance and I fear that I'll have to develop software that is interwoven with many systems and uses Joomla for that. This project is still in negotiation and in the planning phase. The second project is a large freelance project I got, but both are very similar in their outcome. I "attacked" the CMS argument, by saying that there are simple rules for projects: 1. Large Project: Minimal or no base, best to use a framework 2. Regular Project: Small or Medium sized CMS 3. Small Project: From scratch, or with the help of a library. But there is one problem with this. You have to know in advance how much stuff you will add to the initial project, which is almost never the case. And successful "regular projects" almost always get extended. My experience is that people use the CMS Interface rarely or never and a CMS makes developing features harder. I know CMS with an API system that allows the Content to be edited/used from inside of other applications. What should I do? I thought about using a minimal Markdown based Flat-File CMS and to extend that, but then there is the problem of support. Small projects like that are mostly short-lived.