I think some of the neighbours who identified crying and a man's screams will be useful to the Defence. While several people all testified they heard a woman's screams, OP's next door neighbour, (and the only person who knew OP) identified the voice as OP. Surely, he will be key witness for the Defence.
A sound expert who shows OP can scream like a woman, or suggest that it's possible his voice could have been mistaken for a woman's by several witnesses.
Expert testimony that he was on his prostheses when he wielded the cricket bat.
A psychologist who can testify to his state of mind and his heightened fear (as someone disabled) 'imagining an intruder entering the house'.
Although Dixon's testimony may have been laughable at times, he highlighted a couple of ways in which the Stipp's testimony can help the Defence. Firstly, when Mr Stipp saw a bare chested man walking in the bathroom it is likely that OP was on his prosthesis - this was before the second set of noises and is very good for the Defense.
Secondly, Dixon showed that with the toilet door slightly ajar, there was a dim light through the toilet window. Mrs Stipp was adamant about seeing this. I'm sure the Defence will argue that a similar effect could be achieved with light emanating through the bullet holes in the door. And, if Reeva had been alive at that time (as the Prosecution suggest - with light emanating through cricket bat strikes), some sort of movement, or her silhouette would have been seen by Annette Stipp, who was on the balcony almost the entire time between the two sets of noises.