I think the best option here is trying to provide better defaults for the use of CUPS.
The main problem we face is that one of the libraries we use to generate the available printers is broken, and by now, it's too much work to fix that.
If you do configure your printer with CUPS, eBox will be able to see it and share it through samba, so there's no need to allow external connections from CUPS.
But yep, I think that more doc on this and more sane defaults is the only sane approach we can take for 1.4.