I've done ABZ-FRA a number of times and there has never been more than a handful of FRA terminating pax, always a stream up the escalators to flight connections. BM do BRS-FRA with a LH tie-in but I just can't see anyone taking it up.
Best bet for ABZ is for KLM and AF to go back up to 5x & 3x daily respectively and that will fill the capacity void being created. An extra 737 & E170 daily is all it will take to replace LH (I know that's not quite exactly how it works!)