I don't know where this rumour about the 60Da being unsuitable for terrestrial photography started?
To my mind it would be insane for Canon to release a modified body at almost twice the price of the vanilla 60D with no option for 'daytime' shooting.
It's a simple white balance adjustment and there would certainly be a pre-set option for it in the menu.
Not speaking from experience unfortunately, my 60Da body was supposed to be here Thursday.. still waiting