It's the same syntax, and you're suggesting that it be added to the existing function declarations.
I'm suggesting that there is a language symmetry (and simplicity) to be gained by limiting the addition to only named arguments:
myfunc{my_arg = "hello"}
and
local myfunc = function{my_arg = "howdy", arg2 = "good bye"}
---do stuff
end
..just seems like it should be true.
Perhaps it's simpler to apply to every function declaration, as you're suggesting. I think it may be the exact same syntax, other than that.