That would be nirvana! To be able to choose the features/options on first boot up.Skins and services are nearly the only ways manufacturers using Android can differentiate themselves from their competitors since the hardware differences have become so slight.
I'm with you on your desire to have a choice to use an OEM's skin but understand why they don't do it. My frustration with Android stems from this issue. All too often, the phone with my desired hardware specs/design uses software that I don't like (Samsung) or vice versa (Motorola, HTC). I have yet to find the ideal blend of both hardware and software. Having the ability to choose my software experience would be ideal--just don't expect it to happen anytime soon, if ever.
I know there are some ROMs like that now that brings you though a menu and you can pick and choose the features and options you would like to have.