The main reason that many manufacturers (aircraft as well as missiles) use a theoretical station 0 that is located well out in front of the vehicle itself is to allow for future versions.

If you put the origin of your coordinate system exactly on the point of the nose, then any time you have a revision of the nose shape, or a growth/stretch version, or any other significant change, you would have to go through the entire drawing system and generate a new set of location dimensions for all parts, as well as re-numbering the mass properties database, and a lot of other paperwork revisions.

Almost all vehicle config changes will still be using almost all of the previous vehicle parts, so why make yourself have to do a bunch of extra work?

Placing station 0 out in front of the nose by two inches or two miles does not matter, as long as you know the definition of your coordinate axes.

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NAR 20602
used to be "powderburner" in another life