The main issue is the gas price. Even if we reduce the gas costs, the tx fee would still be too large for most of our potential users. So we need a dispute resolution system that can run entirely on xDai. The AMB bridge is interesting idea but it’s complicated and doing arbitration is still expensive in that case.
The reality.eth game really is designed such that the cost of arbitration shouldn’t matter to people who are honest+correct, it actually works better if arbitration is expensive. However to work you do require that someone would be prepared to front the capital needed to challenge a wrong answer up to the cost of arbitration (plus gas costs). That doesn’t need to be all of your users - it’s designed so that A can put in an answer with the correct answer, get in a bidding war with B up to a certain point then drop out, but then richer-person C can take over and start paying higher bonds for the answer that A was giving, Provided Kleros rules in their favour (or B gives up) both A and C will make money in that situation.