GetProperty had a bug that should be fixed in the next build.
In terms of the original issue, it is basically adding a translation facility for images. This is a request that has been around for a long time:-
Bug 1895 - Expand module translation mechanism to include images
It would be better to handle this as a translation issue than having every person roll their own. It is something I have been meaning to get back to.
Sounds like a reasonable suggestion. I have added
Bug 4717 - Change Layer Follow Property name to be an Expression.
Any other places you have noticed would benefit by allowing an in-line expression?