More authority files?
It would be helpful to have more authority files, both to guide data capture and as general reference. Two examples which come to mind are regiments and places.
A searchable hyperlinked overview of the structure of the British Army would be helpful when trying to decide if the regiment (or part thereof) mentioned in an external source matches the regiment recorded in the War Medal data. (I'm assuming that the IWM already has such a resource.)
For place names, we are very much left on our own when deciding what to record, and the result will be anarchy. Can't you include a widget which links to an external authority like Geonames, and brings up suggestions as you type?
Luke Smith commented
These are excellent suggestions.
Name authorities are part of our plans, but we have a lot of features to deliver, so we can't commit to when. We understand the issues of merging free text names with, say, geonames. Others have tackled them before us. We have decided to go live with a core feature set and improve it based on what people do with the site. Much the same applies to an 'order of battle' or similar.
Ultimately, this is the responsibility of the inputter. Place names can always be googled.
For infantry regiments, I would advise looking at 1914-1918.net This came in useful when trying to decipher the battalion on the service record. I could not tell if it was 11th or 21st Battalion, and this site was able to advise that a. the regiment did not have a 21st battalion, and b. that the 11th battalion was in the theatre of war as indicated by the medal index card.