LH will probably be better off operating something larger than a CRJ twice a day to FRA, prob better off with something with 80ish seats maybe an AR8. Bacon did well with a single 50 seat a/c, with a twice daily 50 seat a/c you'd be able to fill on just point to point without the connections, so 2 or 3 per day on larger a/c required. If BHX can fill 4 daily 733's, BRS can surely fill 3 daily AR8's or CR7's.
Muc will prob work well on 2 x daily CRJ's with the connecting traffic too.