Well yes you are right maybe that should be removed once and for all... Having that option in preinit messes up the VOIP and in Harmattan you cannot really access the device via SSH until fairly late stage of boot, it's better to get to the device via seral adapter and R&D mode*if that is required.
First thing that comes up my mind is tagging the place in the preinit with some nice symbol, something like G_IP_ADDRESS_TO_BE_ASSIGNED and then in ubiboot domain to run sed on the file and replace that with the desired address. That would work just once, though as of course on the second run it had already been changed. Having a bit more complex sed script, you could well have a marker there to signify the place of replacement so that is leaves the marker section there for subsequent runs. Possible, but is it useful for many people?