I have purchased 3 anthenna wifi card, but I have only main and aux, but I have WWAN anthenna that I am actually not using.
What do you think ?

No harm in trying.
Those cards also work with only 2 antennae, although maybe not at full strength.
And there is always the 2-wire version Intel 6200 N (MiniPCIe half-size).

So, it is working without problems.

^^^
are you getting full "n" speeds configured this way?
i may try the same thing in my t60p, since i don't use the wwan right now anyway.

thx.