The problem is the cost of doing this. If it gets overturned, the defendant shouldn’t be the one to bear the cost. I’d be happy with either 1) the patent owner or 2) the patent office, who didn’t do its job properly.
The UK and USA patent offices, I understand, have procedures to file evidence showing a patent application is not valid - eg because of the 'invention' already being known.
Your comment seems to relate more to unfairness in [lack of] awards of costs in USA legal proceedings.
If you sue me for something I didn't do then it shouldn't cost me anything; that seems reasonable whether the domain is IPR or any other aspect of life.
This varies between countries. AFAIK it is far harder to get the other side to pay your costs if you successfully defend a case in the US than it is in the UK.
