Yes that would work,
However I kind of want my customers to use the template.


And that would be to much work.

Is there a way to have a log-in function that would then auto-populate the template? Based on their Unique ID

Is it possible? Yes.

Can it be done with a built-in Word function without programming? No.

Is such programming trivial? No. Not in this case. You would want to not only allow the customer to populate it, but also to protect your database from them getting everyone else's data.

This is better handled from the Access end. It could generate merge with a Word template and fill in the information. I do not know how to do that, but believe it would be much easier than trying to protect your database from Word's end.