That's why personally, I'd go backwards and accept only default setup in frameworks.yaml, rather than creating a new convoluted syntax. And we would decide "customizations" only for the franeworks_yyyyQn.yaml ones.
Some frameworks have modes and we don't want additional custom definitions in frameworks.yaml simply for invoking different modes.
By Seb, see also #455:
Some frameworks have modes and we don't want additional custom definitions in
frameworks.yamlsimply for invoking different modes.