As of Netbox 2.10 it's possible to set field validation on custom fields for min/max/regex values.
We should convert the same functionalities that we currently check as part of reports directly into the validation of the fields to prevent in the first place the wrong data to be inserted.
See also:
https://github.com/netbox-community/netbox/commit/8781cf1c57405ee7248a8fff4cbdadec74bf6e7c