The alt key can not be changed in-game, but you could use a keyboard remapper (see below) to change keys before you start the game, and restore them afterward, or a program like
AutoHotkey to do it on-the-fly (this program can also re-map mouse buttons). I have not tried any of these programs (found in a quick search).
MS Keyboard Layout Creator /
KeyTweak /
OkayKeybees /
SharpKeys
