If you are portfolio building it would be daft to take on a wedding which didn't allow you to use the images. Regardless as to whether you were doing it for free at a reduced rate it would be a poor decision to take it on.
With regards the second point I've never not gor a wedding because I hadn't shot at the venue before. Aside from anything else you can only determine there is a loss if it you can substantiate it. Otherwise you're just guessing that you may have lost money... perhaps.
A model release isn't a right... it is a bonus.
I see both sides of this. Early on you need experience as well as portfolio. You don't start out with 100 weddings behind you, and setting a precedent so early on makes it even harder to build the portfolio up. One bride gets privacy at no charge...why not everyone?
Not taking the wedding on would be equally daft as far as the B to be is concerned. It makes OP look insane for turning down work and money over something so "trivial" and a fee also makes OP look selfish.
Not much of a win here for OP if he is relatively new.