Don't u think the way u get the mangekyo sharingan is a bit lame .. i mean how is killing someone dear of watching them die related to a change of chakra of whatever iside the body to produce a new ninjutsu weapon ?

Emotions can effect your body dramatically. People can literally die of grief. All the process for obtaining the Mangekyo Sharingan is is a multiplied version of obtaining a normal Sharingan for the first time. A powerful emotion, usually fear of pain, causes some kind of reaction in the the body that activates the Uchiha bloodlimit.

It's the emotion killing your best friend causes that gives u the Mangekyo, not the act itself.

*Spoiler*
That's why Sasuke's didn't activate his until Tobi told him the truth about Itachi instead of just right after Itachi died.
*Spoiler end*