I’m in favor of this feature. Especially with the elegant pass param syntax suggested by @orise. Reminds me of why I really like inherit in Nix.
That being said, if choosing between param= and =param, I very strongly vote for =param due to readability. I think param= could be become hard to spot with long param names, which is ironically the one time you would really want this feature.
This syntax should immediately stand out when skimming code due to the implications of forgetting to change an invocation using implicit named args when the function signature changes.