Desmond, Altair, Ezio, they're not the same person.

A thing that some people were having troubles with.. I roleplay regularly as Desmond, who was able to tap into his Ancestor's memories and is now able to transform into him completely (Not really, that's more of a fan-add on for me). So when Desmond transforms into Altair, he becomes Altair, he is no longer Desmond Miles. Also, each form except for Desmond has a strength. For instance;

Desmond can only use his Hidden Blade, Fists, and weapons he grabs from enemies with Disarm (A skill which will be made later).

Altair can use a Hidden Blade, Throwing Knives, and a Short Sword, and a Long Sword.

Ezio can use TWO Hidden Blades, a Short Sword, a Long Sword, a Hidden Gun, Weapons he grabs from enemies with Disarm (A skill which will be made later), Throwing Knives, Poison Dagger, and Smoke Bombs.