Well - I know nothing about how GW organises its stock to go to the stores....but it seems to me that prior to a run of anything, they should ask for:-
1 Expected client demand
2 Expected staff demand
Now, this should all be totted up and a check made to ensure that stores are not over / under ordering. This should occur for every product sold whether WFB, 40k, LOTR etc. GW's release schedule is not so massive that this would be too difficult. A standard electronic form from each store / sales channel can be easily collated.
Then a review should be made of number of sales of similar items from mail order in the past year or so (eg how many Amazon teams were sold to gauge how many Khemri to cast / how many BB Mags 1 and 2 for BB Mag 3 etc).
Each of the GW universes (eg GW US, GW UK) should do this if the stuff is printed / cast centrally.
Once this has been done, they should then get the runs done (depending on cost they should get some extras done too) and sent out to the stores / held for mail order.
Finally, every 6 months (actually monthly is better......) each store should be monitored against orders and sales.
Easy Peasy.
Now, perhaps I've missed something here..... if so, I would be delighted to be shot down by Andy H or someone else in the know. But in this day and age of electronic commumication, it should be very straight forward to set up a standard order / stock control system. I know that GW have just introduced a new system of some sorts - but - it seems to me that it doesn't link orders to sales and run variance analysis. Surely GW are not running a "we'll send 5 copies of everything to each store" policy!
As for the staff - sure its a bit naughty for them to buy up the mags delivered. However, the real problem is Head Office / the sales system which does not function properly (or at the least is not being used properly).
Perhaps GW would like to offer me a job?

[Finance consultancy in the City is a bit slow at the moment so I do have some spare time!]
Dave