The daily cron job debug output is really minimal and not useful for actually debugging problems. The old cron did a lot better in verbose mode of telling you everything it was doing and helping to track down issues.
It would really help me as a WHMCS administrator and developer to have a more verbose mode that actually lists what it's doing and outputs debug information, particularly outputs PHP errors and notices / doesn't squelch them. But also outputting each Invoice it is creating, each email it is sending, etc. (at least Invoice IDs and and other relevant IDs) would be extremely in helpful in tracking down where the cron was when it crashed, and hopefully outputting errors.