What a terrible design. Why on earth would you scale back the clock speed when there is actually less load on the charger? Do they use the battery as some kind of heatsink?
I've never had an issue with brown-outs either, but then again I live in the UK where we don't have many and even when we do our line voltage is 230V RMS. Most laptops have universal voltage power supplies so dropping to 120V is no problem. In fact I'm surprised it's much of an issue in the US, considering that such PSUs are normally capable of running on Japanese 100V systems down to 90V (-10%). Does every desktop need a UPS as well?
With the laptop sat stationary on a desk pulling the charger out shouldn't be a big issue. I guess maybe the magsafe magnets need to be a bit stronger. Most laptops don't have gaps where the battery is to let in dust, and if anything would eject it there due to positive pressure created by the cooling fan. The old Macs used to be like that, but I have not taken recent one apart.