Let me clear you point blank Dual Benefit is Not allowed in the Income Tax Act. The Idea behing HRA is to give relief to those who are staying in Rented accomodation. You can not claim the benefit of HRA and Int. on housing loan at the same time. If you are very keen to do so then change your city where your house is situated then you will be allowed deduction on Interes/ Principal and HRA.
Even if you pay off you housing loan you will not be given benefit of HRA as long as your name is appearing as owner of the house.
Also, if you file you show payment of Rent to your wife which she bought even though she does not have any income. the provison of Clubbing may be attracted (Depends on the ITO how deeply he scrutinise your Return, if by chance your return is selected for scrutiny).