All true, but there remains the problem of a symbol that's already assigned to Bitcoin; BTC. The dollar, USD uses $ for each and every amount. It wouldn't make much sense to have two symbols for Bitcoin; the already famous BTC and another one for "Finney." Each price now and in the future is written in BTC. Do you want to change this?
BTW A cent is in fact a dollarcent; for me a cent is a Eurocent.
I'm sure the metric prefixes and symbology aren't going to change, but perhaps informal or colloquial terms will eventually emerge for the milliBTC and microBTC units. For example, we all agree that a "satoshi" is 0.00000001 BTC, 0.00001 milliBTC, or 0.01 microBTC, without needing a new symbol for it.