Unique, well, that's a strong word. So, I must vote no. As to what people may think unique:
Ki: Philosophically, explicitly part of the Chinese arts, and as to following flow and momentum (energy), quite common.
Off-the-line: My background (in addtion to Aikido) is western sword arts. Off-the-line is near univeral in their martial application. The modern linear sport fencing mat does not reflect the martial tradition.
Love: Not speaking Italian, I can't precisely quote, but Fiore de Liberi, (15th century) says that one must practice with love towards your partner in your heart. While I don't know of others explicitly saying this, it is probably near univeral in all weapons training halls. Weapons are dangerous, no other attitude really works for training in their presence.
Religion: Fiore (obviously Christian) repetedly says "I will show you how to use the cross to protect you" refering to crossed sword wards and binds, revealing his underlying devotion. Religion is a common basis for almost every medieval mindset. O'Sensei certainly had no monopoly on devotion. As another (old or modern as you chose) example, Systema has a religious component.
Body art based on swordsmanship: Most western sword combat traditions have integrated grappling. They simply go together for anyone who can acquire weapons. If one is a trained swordsman, one will move as such and your grappling will reflect it.
Other: Please suggest. I love Aikido, so if anyone can prove philosophical uniqueness, I'de love to hear.