Please don't hurt me, but I have no problem with calling unmodified SHIII 'stock'.
One of the definitions of the word 'stock' is just that: Unmodified.
10.the person from whom a given line of descent is derived; the original progenitor.
43.of the common or ordinary type; in common use: a stock argument.
44.banal; commonplace: a stock remark.
The raw material out of which something is made.
3. regularly and widely used or sold; "a standard size"; "a stock item"
As for the use of 'Vanilla', I point you to the 'New Hackers Dictionary':
http://www.ccil.org/jargon/jargon_37.html#SEC44
vanilla /adj./
[from the default flavor of ice cream in the U.S.] Ordinary flavor, standard. When used of food, very often does not mean that the food is flavored with vanilla extract! For example, `vanilla wonton soup' means ordinary wonton soup, as opposed to hot-and-sour wonton soup. Applied to hardware and software, as in "Vanilla Version 7 Unix can't run on a vanilla 11/34." Also used to orthogonalize chip nomenclature; for instance, a 74V00 means what TI calls a 7400, as distinct from a 74LS00, etc. This word differs from canonical in that the latter means `default', whereas vanilla simply means `ordinary'. For example, when hackers go on a great-wall, hot-and-sour soup is the canonical soup to get (because that is what most of them usually order) even though it isn't the vanilla (wonton) soup.
In the sense it is used to describe unmodified SHIII, the term 'vanilla' is perfectly appropriate,
given the intended audience (ie., mostly geeky males, present company excepted).