3.16: Bad-Weather Visibility: It's your job to figure out which bad-weather visibility aids will be most useful for your car. Wipers, Rain-X, tearoffs, small squeegee-wielding children tied to the hood, etc. are all acceptable.
Just make sure the squeegee is restrained by a lanyard so it can't get dropped. If it was dropped you'd simply then have a small child tied to the hood - not acceptable. I would apply the 'etc' part in the execution of the rule in that I'd tie them to the roof, so that in the act of squeegeeing they don't compromise your view hence causing you to fall foul of the "visibility appears compromised during the race for any reason, you may be black-flagged until conditions improve." language within the rule.
Of course all the preceding in my reply is intended to be only read and in no way to be implemented in the real world.