All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
There is no disagreement among the scholars about the recommendation of adorning oneself for prayers in general and for the Friday prayer in particular. This recommendation includes the Imaam, the Khateeb, or anyone else. Each person is required to adorn himself with respect to clothing, scent and other matters that enhance the appearance of the worshipper. However, there is no specific outfit that is conditioned for the Imaam or the Khateeb to wear. Moreover, they are not obliged to wear a turban. Nonetheless, it is recommended for them to cover their head, whether with a turban or with anything else. If they performed the prayer bareheaded, their prayer is valid as well as the prayer of the worshippers led in the prayer by them, as agreed upon by the scholars.
Likewise, it is not a condition for the Imaam or anyone else to wear a cloak during the prayer. However, if it is the custom of the locals to wear it to adorn themselves, then it is recommended.
Therefore, there is no harm if the Imaam or anyone else prays in a jacket and trousers if the latter is not tight fitting and does not define the parts of the body that should be covered. If the trousers are tight fitting, then it is disliked to pray in them. However, if the jacket or shirt drapes in such a way that it covers what should be covered, then there is nothing disliked about it.
Allaah Knows best.