Probably asked before but, can he use BT when his Perplex clicks come up, can he use BT?

Yes, but only if an Opposing character is KOed.

Although the character does not need to be showing outwit, they would still need the use of outwit on the dial. I would say as long as an Opposing Character has been KO'd then the qualifications for being able to use outwit are there and therefore you can use Brilliant Tactician.

The text seems to be a very fine line. He doesn't need to be able to use Outwit, nor does he need it to be showing when BT is used. I question why people think he needs to be able to use it when he tries to BT.

A character must be able to use a feat in order for it to be a prerequisite for a feat.

True, BT makes a point of saying Outwit doesn't actually need to be showing in the dial slot, but the character must still be able to somehow or another use Outwit at some point in the dial.

Unless an opposing character was KO'd, MM can't use Outwit. Ever. Spin that dial as much as you like and Outwit isn't available. Only a KO will allow it to be used.

This goes for any conditional power: If SI Namor wants to use Automatic Regeneration, he needs to actually occupy Water terrain.

Aquatic Rejuvenation: If Namor occupies water terrain, he can use Regeneration.