PlotBands require an axis and two values from/to.
I think can be a good idea to extend some features:

1) If to is null band can stretch in positive axis direction
2) If from is null band can stretch in negative in axis direction
3) If to and from are both null plot band fill the chart area

4) Plot band can accept also axis2, from2, to2 parameters, if defined, plot band stop in axis2 direction instead of stretch,

Here a demo prepared by mateuszkornecki
https://jsfiddle.net/BlackLabel/z9hxgrd1/

Thanks.
marc.