Re dibbers: beware. Riders will lose them, and then they are in trouble. A brevet can be mislaid - and as I saw with one rider - the stamps can be collected on a piece of paper until rider and brevet are reunited and all is well again. You will still need a person sitting at the dibber box, so no saving on staff there. And as we saw, the software can sometimes go a bit awry, and a stamped brevet, hung round the neck of a rider and in a waterproof bag, is a pretty bomb-proof way of proving where you have been. Dibbers work well when you need to know timing to the second, which we don't on LEL.
FWIW, IMHO, change nothing. You mess with the 2013 LEL format at your peril. Using schools as controls worked well, the date was fine (in school holidays so school premises were vacant and people could take part if they or spouses were teachers), the route was as good as it could be, and the food - using the professional chefs - seems to have gone down really well.
My only minor suggestion would be to employ professional cleaners, perhaps those who normally work at the school, to free volunteers so they can do the "interaction with riders" bit, because that is where the event seems to have really shone. If necessary, put the price up. People flying in from Kyrgystan, Taiwan, Canada, or getting the train from the Lake District, are unlikely to be put off by another £30 or so on the price.