So the first problem was a rookie mistake on my part - NSIS installers need capitalized switches!
Then I ran into the code 1223 problem, and the IDE appeared to install fine so I just told Altiris to consider 1223 a success.
So I installed the SDK using /S /AllUsers and installed the registry key, but when I run the android update sdk tool, it seems to want to re-download all of that from Google, which would mean it would be doing it for every machine. This seems to defeat the purpose of deploying the SDK in the first place, no?