As far as I can see, there is nothing wrong with using the P3 gamut to edit for print. It is approximately the same size as aRGB and covers most of the same colors. With either gamut, there can be colors that could show in an inkjet print that they cannot show.
On the one hand, it is unfortunate that Apple does not make a computer alternative between the Mini and the Pro that does not include a monitor. On the other, the retina monitor can be useful as a reference for what many viewers might be looking at on the Web these days.
As far as a video editing standard, I wonder how many serious video editors would rely on an iMac for that.