Instead of hacking text files,
I would not call this hacking text files. This is a simple structured configuration file. If your programmer happens to be and avrispmkii it is a simple as adding the following lines to hardware/arduino/boards.txt:
# this defines how the entry will show up in the IDE menu
atmega328ispmk2.name=Arduino ATmega328 AvrISPmkII
# maximum upload size = maximum flash size since we do not need a bootloader anymore
atmega328ispmk2.upload.maximum_size=32768
# which programmer to use
# avrispmkii exists already in programmers.txt
# if you possess a different one you might need to add an entry there as well
atmega328ispmk2.upload.using=avrispmkii
# target controller, relevant for the controller AND the compiler
atmega328ispmk2.build.mcu=atmega328p
# target frequency, irrelevant for the programmer, will be picked up by the compiler though
atmega328ispmk2.build.f_cpu=16000000L
#atmega328ispmk2.build.f_cpu=1000000L
# no clue what this does but the other entries use this as well :)
atmega328ispmk2.build.core=arduino
It is really simple. In my opinion this does not at all qualify as hacking. Especially it paves the way for other controllers as well. Once you start thinking about it this bascially opens a whole new world. You do not need to stick to any Arduino boards whatsoever. This way you can flash any "naked" chip right from the IDE. Just look up the datasheet for the default speed and flash size and stick to the RC oscillator. Unless you need really accurate timing this is the barest bare bones operation you can achieve
Udo