It seems like a lot to me, even if it doesn't to you. This is because I generally play SP with fewer starting Civs than 16 (usually about half that) on Huge maps or larger. On the other hand, this is "your" game, so I will have to bend to your preferences. I am reasonably certain that all the units involved met all those criteria and there was no merge button. However, it was a while ago, and I may be forgetting something and/or may have overlooked something at the time. Would it be possible to have the Merge button appear all the time, and list exactly what does not match if it is not usable at that moment? As it is, it can be frustrating with not having a reference in-game.