The possibility to set the minsize for a file, that should be rotated, would be nice!
See here the logrotate docs: http://linux.die.net/man/8/logrotate
minsize size
Log files are rotated when they grow bigger than size bytes, but not before the additionally specified time interval (daily, weekly, monthly, or yearly). The related size
option is similar except that it is mutually exclusive with the time interval options, and it causes log files to be rotated without regard for the last rotation time.
When minsize is used, both the size and timestamp of a log file are considered.
Nice idea - I will add this in the next Webmin release.