I think your point about trying to do something different is a good one, Miss Ross - there are facets to previous ones which have made me uneasy about attempting to get to forums concerts, and clearly a Scottish one would reduce the travelling problem for me.
This will sound terribly negative - I don't mean it to, but I would be put off by things like obligatory singing, massed recorders and an unrehearsed grand finale item comprising whatever turns up on the day - yes, music-making is about the pleasure of communal activity as well as what so many of us end up having to do to learn our instruments - ie, plodding along on our own ironing out the squeaks and intonation problems - but concerts are usually about presenting something we have polished to the best of our ability, and it can be an uncomfortable thing to have to listen to too many items which are under-rehearsed. This sounds as if I'm demanding professional standards of playing: I'm not - there is a difference between the slips musicians make because they're nervous, and those made because they're quite simply not on top of the music.
The advantage of having such regional get-togethers is that musicians who live in reach of each other but might not think to meet up can have some stimulus to do so, and practise something together - I know that I welcome the oppportunities to do this for concerts and workshops I've been lucky enough to be asked to play in. It's about more than just the music on the day, it's about the whole process of making music. I think it would be wise to let the less experienced and more nervous contributors go first, the more accomplished and laid-back last, to save people from comparing themselves to others too much.
Finally, a positive suggestion in all this - perhaps a common theme for the concert? Say, animals, or travel, dances or plants? As long as not everyone wants to play the Flight of the Bumblebee, of course

.