RE: re: scenario design
I think the most difficult issue around orders of battle is the amount of incomplete, confusing and/or contradictory information, especially if one is researching the defeated (where records are lost), a lesser known combatant (eg Albania),or a combatant with a small administrative tail (eg Viet Cong). Governments will not infrequently hide or modify the truth.
The more sources one consults, the more likely one is, I think, to approach the truth. There is an argument for specialising in a particular field, if that appeals. Wikipedia, I have found, will generally be right more often than wrong.
The computer allows us to hugely expand our scope with its translation facility. I have recently used this to look at sources which are apparently not available in English. These gave me enough info for a credible OOB. Which, I hope, is enough.