You will get lots of different opinions on this. Mine is no, don't do it. The purple, chevron and powder blue are territorial and mean. In the long run, I believe the powder blue would end up king douche of the tank.
80g is marginally large enough for one of those. I have one chevron in my 100g and I've had a purple tang, though not at the same time. I've been keeping fish over 40 years and have never seen such territoriality as I saw out of my chevron when I added a flame hawkfish (and I've kept African cichlids). The chevron even slashed the hawk with his knives. Mean, territorial, aggressive, persistent, intolerant aren't sufficiently strong as adjectives to describe the intensity of the chevron's intruder defense behavior.