I'm unsure about the gun and random inventions.
To me AC was great because he was using very basic weapons, and a lot of skill, if he starts running around with all kinds of crazy contraptions then it kinda loses its theme for me :3
No not really. I forget how, but once you learned how to do the parry-to-kill combo the game was pretty easy, even when faced with like 8 people. If he runs around with crazy contraptions, then he's probably way more 'assassin' then running around with a sword and jumping into an open area and parry-killing. Really now..