Several of Magma Dragoon's attacks mirror that of various characters from the Street Fighter series, including the well known "hadouken".
Originally, Zero was going to have an ultimate armour similar to X's armour, but due to various circumstances it was dropped. Little is know about the armour, except that it was meant to connect him back to Spoiler:Dr. Wily.
If you look at the symbols on the bosses health bars, three of them have the normal Sigma symbol (Magma Dragoon, Cyber Peacock, and Split Mushroom), while the other five have the symbol of the Repliforce (Web Spider, Storm Owl, Frost Walrus, Jet Stingray, and Slash Beast). This means that most of the bosses you fight have not turned Maverick like the other games.