Standing after losing - presumably losing consciousness is a very symbolic thing. It's obviously Oda's way of preserving Lucci's perceived honor or respectableness as a combatant. It's Lucci's subconscious way of saying "You haven't seen the last of me!". Defiant to the very end.
In other words, this is an absolute proof that Oda has a lot of love for Lucci. Only other character with something similar is Whitebeard, though he died standing so its different.
If Lucci retained consciousness and still dialogues with Zoro somewhat - Lucci will still look good.
If Lucci lost consciousness, due to the symbolic nature of the unique loss - Lucci will still look good.