Primary keys as Calculation

Hi, we are setting up a server to server mirror sync. Today we do not really use Primary keys. We use keys but they are not guaranteed unique. I used a calculated field with UUID to get a Primary key.  But since I used a calculation i cannot really check the boxes "Prohibit modification of value during data entry" or "Unique value". Is there any problem doing it this way?

"If you are using UUID primary keys, be sure to UNCHECK the field options checkboxes that say 'Do not replace existing value of field' and 'Prohibit modification of value during data entry'. Enable the 'Unique value' validation option."

Thanks 

Mikael