Internal door framing idea

[incognitotheone]

I am about to change my internal doors upstairs. They are old design with a window above doors (previous owner did hide them behind mdf) and frames are going all the way up above ceiling level into the loft.

I removed one of them as we were moving a wall and it was proper pain in the a.. . Walls are breeze block type, so there will be a lot fixing when I remove door frame. So I was thinking about leaving sides of old door frame (taking out window) and fixing new frame into old one. Obviously I would have to use slightly smaller doors but that is not a problem for me.

Is my idea viable one? Or will this create a lot of problems?

 

[foxhole]

If you are happy with smaller doors then no problem.