Security is, of course, a most vital concern.
But, as they evolve, technologies inherently become more vulnerable. (As do organisms for that matter — a jellyfish can't die of pneumonia.)
So, in order for the candidate to survive, the newly gained strengths must outweigh the newly gained weaknesses.
Apple uses WebDAV extensively.
I'm sure they are a security aware company.
How do they do it?
This is surely a most sensible approach!
On the other hand, not allowing for gradual transitions bears the possibility of stagnation, as every so little modification becomes a gigantic undertaking and therefore often tends to be better left alone.
How, for example, will you ever upgrade to PHP5 this way? (Or will you just not?)
But I am going too far!
I don't have any experience running a commercial web server, and thus no qualification questioning the way you run yours.
Please, accept my apology if I have unduly criticized you, as I realize I am over my head here.
My initial post was not intended to conjure up a discussion about your policies and as I said there: I am generally a very satisfied customer of yours!
I may, at times, be too easily enthusiastic about new technologies. I just like to see good things get better and, as everybody else, would love to have my cake and eat it.