It also doesn't help that when some people say restricted shell they mean "actually like bash, running on a real system", or more of a debugging console (a besp

It also doesn't help that when some people say restricted shell they mean "actually like bash, running on a real system", or more of a debugging console (a bespoke REPL a la Python's stdlib's cmd module). I'd happily believe you can secure something like the latter, and I don't think it's worth the expense of securing the former. (But also, if you give people an anodyne shell like that, what's the point? If all you can do is peek and poke at metrics then maybe you just wanted better instrumentation?)