I think you can now have one or even two Par 5s and it would be very good -- because you'd already envisioned them as *Par 4s*.
I think that might be the key to building a very good Par 5, i.e. don't start off trying to build one.
The run-of-the-mill Par 5s, the thousands of average ones scattered across the land, were all planned as Par 5s right off the bat, with all that this functionally entails (e.g. using up some ground, upping the total yardage, fitting the usual pattern/model of Pars, giving the hacks a chance at a birdie putt etc) and that it usually results in, i.e. not a very good golf hole, and a boring 2nd shot, and a very large green with one shelf.
Peter