Can he rent the traditional set of jewellery and then return it to the jeweller in order to get married?

Praise be to Allah.

Firstly: 

The Standing Committee was asked a similar question, about renting gold and silver jewellery for the woman to wear for her wedding, then returning it two weeks later, for example, and paying for that. They replied: 

The basic principle is that it is permissible to rent gold and silver jewellery for one of the two currencies, or for something else, for a known rent and period of time, after which the one who rents the jewellery is to return it. And there is nothing wrong with taking collateral for that. 

Fataawa al-Lajnah al-Daa’imah, 15/79-80 

The two currencies are gold and silver, i.e., it is permissible to pay the rental fee in gold or silver, or in the banknotes that people use nowadays. And Allaah knows best. 

Secondly: 

Women’s fathers and guardians are advised not to make excessive demands with regard to the mahr (dowry), and not to burden prospective husbands with unreasonable demands as regards the mahr, traditional set of jewellery and furniture, etc. Such excessive demands are condemned in sharee’ah, as are the harmful consequences to which they lead. See question no. [12572].