I can't imagine the circumstance where this would be a good idea. Could you elaborate as to your reasoning?
Perhaps there's something unique about your situation(?)
To the BP, you represent the face of the people taking away their child. Taking away.. as in steal. they won't necessarily trust you. They may see you as competition for their kid. Someone using their better station in life to steal their baby (even if the kid is older now, it was their baby at some point).
If the BP is a manipulative sort, they'll see this as in invitation to start messing with you. i know that sounds really harsh. And there are good people involved in the foster care system, but in general - its not your job to engage with nor befriend the BP
If they show commitment to RU, you can establish a relationship at that point. Help mentor as needed
As for a letter to a FK, I personally wouldn't do that.
To start with, it's probably for a MAPP class. But could I get you to explain your thought process on this?
In reality, we as foster parents aren't taking away or stealing their child. We aren't competition, or people trying to use our station in life to steal their children. We're a resource. People who offer support, compassion, empathy, and yes a safe place for their children to be while they're working on getting their life back in order. As for it not being our job to "befriend the birth parents" I think you're wrong. We're a resource, bridge, mentor, and the people loving their children. While primarily there to be the safe space for the child, it's not just the child. In the end we all hope and pray that the kids in our care get to go home to a situation that was better than they left. That means rooting for and being the cheerleader of the birth parents.
As for the letter to our future foster children, why wouldn't you do it?
In my opinion it's the best opener for the potential placements. They get a small feel for you, your home, your community, and a glimpse of the love and safety you can provide.