Oh well I'll argue the toss
If you fill EF up with just 'Scottish' aircraft at the expense of crowd pullers, and the place ends up going under from lack of visitors, how has that helped?
Concorde will pull in piles of extra visitors and bodies through the entrance mean the collection's longer term future is happier. I too don't see the real relevance to the Scottish theme of a Harrier or a Concorde but I can see their relevance to a kid who just wants to go and see some exciting jets. Most children will be far more interested in a Harrier, or going inside a Concorde, than they will be in looking at a second Bulldog that differs from the one they have only in paint job and a few details (child's eyes remember).
Slavish adherence to a particular collecting policy at the expense of crowd-pullers can only ever be a bad thing - and I have little doubt that the building to house Concorde will also house a few other items that would otherwise be stuck outside. I hear, for instance, that the Comet will come indoors too.