atrocious_kwargs.rb

class Binding
  def lvar_hash(*slice)
    (slice.empty? ? self.eval("local_variables") : slice).map { |name| [name, self.local_variable_get(name)] }.to_h
  end
end

class Object
  def send_with(a_binding, method_name, *args, **kwargs, &block)
    kwarg_names = method(:foo).parameters.select { |t,n| [:keyreq, :key].include?(t) }.map(&:last)
    send(method_name, *args, **a_binding.lvar_hash(*kwarg_names).merge(kwargs), &block)
  end
end

usage_example.rb

def foo(a: 1, b: 2, c:)
  p(a: a, b: b, c: c)
end

a = 10
b = 20
c = 30

send_with(binding, :foo)
# -> {:a=>10, :b=>20, :c=>30}

send_with(binding, :foo, c: 300)
# -> {:a=>10, :b=>20, :c=>300}