You can have the best drafted restrictive covenants in the
world. They will be of little or no help if they are not properly
incorporated into the contract of employment.
Similarly, trying to assign the covenants using other methods
can also be problematic.
The 'one size fits all' approach makes it difficult to
establish that the covenants are applicable to specific
individuals.
Or, if you try to incorporate the restrictive covenants into
side letters that could also lead to arguments. Including as to
whether or not there was sufficient consideration to make the
covenants legally binding.
The good news is even if you don't have a signed employment
contract, that isn't necessarily fatal. Often a binding
obligation can be established simply by looking at the conduct of
the parties. (For example, if both parties have been aware of the
terms and complied with them. Even though they have not signed them
off).