During development i have been requested to know the order in which user has performed the selection of mesh data
You can check how has been resolved
http://www.mechanicalblender.org/features/select-order-storage.html
Holy cow and Teutates! Does it really exist?
BMesh is sophisticated … 
Great you got it to work. Epic works your mechanical blender. Keep going comrades.
(Not yet dared to code blender core code because I thought Add-ons might be easier to maintain and be more compatible and more desired by blender developers. My addons suffer from taking too long … I might change my mind.).