We can easily get the Fax and Company Number added, that will be available by the time we push out the next release.
The “time to pay” is tricky as this is calculated dynamically on the client detail screen and there’s a lot of computation going on there (as far as I know). Including that in the backup means running that calculation potentially 1,000s of times in a short period which would put a lot of strain on the database and slow everything down.