What I'd like to have is a parent pom.xml at the root of the project sources importing child pom.xml files "on-demand". Is it achievable using Maven? Say if some other team member creates a new module and puts a child pom.xml in it, then on system build the parent pom.xml imports the child one automatically (without prior modifications done to the parent pom.xml).
No, it doesn't work like this. There is no "automatic" discovery of new modules in multi-module projects. You will need to define the relationship between the child and parent poms in the parent pom.