Before I say anything I want you to know that I don't like doing this, and I'm not doing it to give myself a better chance of winning. I just want to see all of the servants portrayed as accurately as possible.
I've got some issues with Lancer. I love the character in general, with a brief skim over his legend I can tell he's an awesome warrior but I can't help but think he's too strong. You've given him physical stats of A/A/B. To be quite frank that's ridiculous. Fate/Stay Night Lancer and Fate/Apocrypha Lancer of Red are both demigods with lower stats than that, summoned into the same class. This guy, unless I'm missing something, is human and his stats should probably reflect that. Also, the strongest stat for Lancer class servants has always been agility, though if you want to mix that up because your interpretation of your character is different then that's your prerogative.
You also seem to be under the impression that Battle Continuation is a class skill of Lancer. It isn't. Fate/Zero Lancer and both Fate/Apocrypha Lancers don't have it, the only class skill for Lancer class servants is Magic Resistance. That aside, I don't see any reason in his legend for him to have it, though his legend is pretty bare bones so there's not a lot we can pull out of it.
You'll have to explain the "posts" thing with Lancer's spear 'cause I don't get it.
As the spear is ranked A+ should we take that to be it's maximum damage output when used with "For One's Kingdom"? It's acceptable if it is, A+ is damn high.
I'm very hesitant to say the least about calling the poison he's using with his spear EX ranked in potency. That's equivalent in strength to Alexander's entire army, or Gilgamesh's Gate of Babylon. Can you really justify it being that strong?
Other than that the guy sounds really cool. I love the switching between poison and fire on his spear, and his skills sound formidable. I just can't help but feel it's gone a bit overboard.