It would be vital to be able to run Groovy script as part of JCasC configuration. First of all there will be always something, that when Yaml is insufficient and can be done only using Groovy. While we can still run Groovy, by putting them in init.groovy.d, it is reasonable to be able to reload them along JCasC configuration
TBH I would advice against that for production instances until JCasC loading logic is improved. JCasC has a known issue with the initialization lifecycle. JCasC loading may be happening in parallel with Jobs loading, and there may be various race conditions if we run Groovy interpreter with its classloading magic.
TBH I have tested this few dozen times and I did not notice aby issues. Could You try? I have made pull requested #687 with proposed feature. So far IT passed my tests...