The problem, from a
business point of view, is that 7/5/5/4 requires two dropped shifts, and both Lates, which is "expensive" both to roster & fund. It does, however, have the advantage of a 3 week turnround, so you know where you are (take a look at the TFO rosters if you want a complete circadian co*k-up as well as personal planning pandemonium).
Whilst 6/4/7/4 is legal (better if both last Lates finish @0300); & also has the advantage of a 3 week turnround; it is less
comfortable for the regular pilots as it requires them to fill all the Late shifts. It does mean that the business only needs to fill one Day shift per week, which is far easier to manage - the most uncomfortable thing depends on which day the dropped shift falls.
Some units have operated a system not far removed from this for 5+ years without problems, and a "lighter" version for many years before that. This latest iteration is the ultimate version in squeezing as much as possible out of the taxpayer pound, (which is sort-of what NPAS have been charged with, after all) and individuals do need to manage themselves. For those units that normally finish @ 0400 (except for 0300 last Lates) it's more uncomfortable than regular 03 finishes, but there are 6hr flying Late shifts, and there are foggy ones! There's little in the current climate that is as comfortable as it was 10 years ago and, whilst it's not brilliant, I'm with Art - better the Devil you know than 3/3/3!
I feel one of my brackets could be expanded a lot further, but would probably fill another whole thread!