Interesting. I see you're prepared for the worst case :-) However, since I am somewhat lazy, I prefer to have all my services work with standard apt-get'able packages. This may also prevent possible security related problems. I am using the 'database-export-approach' to maintain the configuration files of the various services. This has proved very stable for 3 years now and it allows me to do upgrades the 'apt-get way', without recompiling or modifying source code.
So you are using the approach I am currently working on. I'll be doing extensive error checking since ... sql server(s) not responding/no access, invalid data, etc and after the update i'll send out an email report with all the details.
I'm thinking of using Perl for that, although I'm no Perl expert. The only other solution would be using commandline PHP ...
What do you suggest ?