Recently I've returned to writing scripts using Byron Rakitzis' reimplementation of the Plan 9 rc shell, and been very happy with the results. It doesn't have the idiosyncrasies that bash has, and which seem to be a motivation for bish. Variables are not rescanned when expanded so you don't have to remember hacks like '"$*"', for example. At the same time it adds some features which really help when writing scripts (a list type and a pattern matching operator for example). And yet it still feels like a shell rather than a 'proper' scripting language: pipes and redirection are still core parts of the language rather than things you have to program using the standard library.

It's included in the standard Ubuntu repositories (http://packages.ubuntu.com/trusty/shells/rc) and it looks like it's in homebrew as well. I'd recommend giving it a try. The original Plan 9 paper describing rc is a good place to start and a good read, although you should be aware that Rakitzis' version made some minor changes to the syntax (a more usual if...else instead of Duff's 'if not') and dropped some Plan 9 specific pieces.