Cannot create a basic theme in 4.3 because documented processes don't work

I tried reporting this via your support desk (see https://support.atlassian.com/browse/CSP-92092) but they tell me I need to move this here.

We are trying to upgrade from 2.8, where we had a nice simple theme.

We want even less customisation in in 4.3, but do need to change the menus (eg: remove "Log Out" from the User one, because we use digital certificate SSO).

Problem 1: "simple" mode themeing, as described at https://developer.atlassian.com/display/CONFDEV/Theme+Module doesn't work.
That page has broken links, but one that does work (https://developer.atlassian.com/display/CONFDEV/Creating+a+Stylesheet+Theme) implies you can create a trivial restyling by JAR'ing a handful of files together.
But, if you install the demo .jar it doesn't work (page border and footer are lost).

Problem 2: if we really really have to go down the build-using-SDK route we need documentation that works.
I have listed the troubles in CSP-92092, but the current blocker is that the "atlas-mvn eclipse:eclipse" command fails (see the CSP for errors) with missing files.
Your support desk tells me I need to install these, but I need instructions on how to do so.

Fundamentally someone should write/correct/test your documentation and/or SDK packaging to something that works.