Add primary key in standard table extension

Hi all,

I'm facing the following issue and I'd like to solve it in the most correct way: it's requested to add a primary key in a standard table that currently don't have it.

We can add it in the extension of the table or do it via validateWrite method, but my doubt is that in the future Microsoft can decide to define a primary key that can conflict .

Is there an indication or best practice about it?

In the case we define a primary key there will be a warning for the conflict ?