I totally agree with Indie. I actually think Heather is a great player, and it seems to me that her problem is more mental than physical I have watched her often and she plays some wonderful tennis but just seems incapable of performing at that level on the important points, and is therefore not able to win matches. This is particularly a problem in singles, whereas in doubles where she has a partner she seems much less pressurised and her results reflect this. Playing Fed Cup is the perfect environment for her as she has the support of Anne with her throughout the match as well as a doubles partner and the rest of the team cheering her on. I wouldn't hesitate to pick her as no 1 doubles player and I too would partner her with Harriet. Jo carries the main responsibility of providing singles wins which is more than enough for anyone, and doubles really isn't her forte.
Yes, I would play Heather and Harriet too in the doubles, and I would certainly keep Jo only in the singles. That's enough pressure in itself for her. Heather definitely performs way under her ability because of her nerves, but it's become so ingrained now that it's hard to see how she will escape it in her singles play any longer. She'd need to totally recalibrate her imagination.
Big fan of all three players under consideration, it would be Hev and Hasser for me, I would like to see them play together during the grass court season but that may not work for either of them ie. Hev can normally recruit a high quality partner.
Another Heather and Harriet vote for me. Keep Jo and Katie B fresh for the singles and both have prior doubles success, Heather as our best doubles player on paper and Harriet at Wimbledon as previously mentioned. I'd have Harriet as first singles back up to Jo and Katie B as well.