Ezio's Florence outfit is my favorite outfit in the game. For me, the crossbow and the sword he carry around seem a bit out of place with that outfit.

So here is how to do it:
1. Hold the crossbow in your hand.
2. Find guards,the ones that walk around with pikes.

3.Let them kill you.
4.Do not wait until respawn, when the screen turns white, press ESC as soon as possible.

5.Go to inventory, then wear Altair's Armor.

*When you respawn the crossbow is gone.

How to unequip Sword:
1.Go to a blacksmith, purchase a heavy weapon.
(Mine was called Stocco?)

2. Hold the sword in your hand and hold left click to throw it.

I hope this helps, have a great day everyone.