One thing that I think that the OSR could use is a rules set for mass combat. And it looks like Basic Fantasy RPG is the first to do so! Written by Alexander Macris, he has released a test version and it can be download it here. This isn't the final version, and I haven't previewed it yet but it looks very promising.
***BFRPG is not the first Spellcraft & Swordplay has featured mass combat in it's rules as well as B/X companion has***