The Ice section here could be cleaned up somewhat and greatly simplified.

- install homebrew python
- install homebrew ice

That's it.  So long at you've got /usr/local/bin on the PATH (as homebrew recommends), all the programs, libraries and python modules will be available by default with no additional messing around.

From a historical POV, this doesn't apply to the ome/alt homebrew ice.  But for new installations, using the default homebrew ice, there's no need for it.  These instructions are for new installs, so we could drop all the unnecessary complexity.  As most, it just needs a comment about how to revert to using the homebrew ice.