I think `Aperture` objects should support arrays of apertures (just like e.g. `SkyCoord` and `Time` and other Astropy classes do). It might not be easy e.g. for Polygons of different length ... maybe there one has to use lists and only allow 1d arrays of apertures?
@bsipocz Can you make an issue for this (if there isn't one already) as a place where we can discuss how it should work in detail?