Hi,

I think I have a working implementation of this at
 https://github.com/evgeni/grml-autoconfig/compare/optin_stats
There is a 64bit ISO for testing up at
 http://pinky.die-welt.net/~evgeni/tmp/grml64-opt_in_stats.iso
Ignore the reverences to "KiVS" in there, that are just a couple of addon 
packages installed.

Changes are:
 * the bootparam changed from nostats to stats, and works the other way round 
now (only submit stats when booted with stats)
 * you now get a quickconfig promt that aks to submit the stats
 * you can call "grml-submitstats" at the shell

enjoy