Desmond's motivations in Flash Sideways by DToccs

Here's something interesting I noticed after WTDF. This is from the conversation between Desmond, Sayid and Kate in the paddy wagon.

Desmond : I'm leaving and I can take you too. But before I do, I need you to promise you'll do something for me first.

Sayid : Absolutley I promise

Kate : "nods head"

Desmond : Excellent then we're agreed.

Now if that sounds vaguely familiar it should. Here's a clue Ab Aeterno inside the Black Rock.

MIB : Before I let you out of those chains, I need to know that you will help me . . you promise?

Richard : Yes of course . . . promise

MIB : Then we're agreed.

This got me thinking, we have all been assuming that Desmond's reasons for gathering all the characters together are good, what if we're wrong? So far in the main timeline we have seen MIB spend the entire season trying to gather the losties into one area (the sub) so that he could kill them all at the same time. Maybe just maybe, Desmond in the FST is trying to do the same thing.
Now I'm really sure why he would, maybe he IS MIB in sideways, maybe he has some other reason. But the important thing is that we don't know enough of Desmond's plan to assume it is good. Afterall a lot of people thought MIB had good intentions until he tried to kill everyone.

Just something to think about before the finale.