Fitting a manual transmission would be favourite or you could ask an auto expert to doctor the existing transmission. Trouble is you can't do much without causing lots of fault codes.

Remember reading somewhere, professional bi-directional diagnostic software can change the transmission parameters and even select and hold a particular gear...
It was a warning that was attached to some software that advised users to be careful not to select a low gear while travelling at high speed as it would cause embarrassing and lengthy interviews with irate customers...