The linked DVR/receiver looks interesting, but you see from the YouTube video what people don't like about 5.8! It doesn't penetrate well.
The problem of course is that on a mini-quad, using anything else means using a larger antenna, more weight etc. I can tell you that even a super IPS display is going to bite it in the sun, so unless you're covered with a black cloth shroud (which is going to look pretty strange), FPV with anything but goggles is going to be pretty difficult. Even a shield doesn't work as well as you might think because if your eyes see any appreciable amount of bright light, they adjust down to that and your screen looks like nothing.
I've been looking for goggles without internal receiver(s). I'd happily use a separate receiver (1.256GHz looks good in tests - see what Flite-test did) and find goggles that take an external video signal. If I had goggles with HDMI and composite inputs, that would be ideal.
The Ares Ethos is pretty small. You may just want to relegate that to flight training and fun and build something bigger that can do a lot more.