I know nothing about the 853 or what hydraulic issues you are having. My guess and experience is nobody is going to tell you how to bypass original designs and or safety mechanisms.
I had what I thought was an auxiliary hydraulic issue on a 773 recently. I think there is a logical approach to troubleshooting your problem. It could be as simple as an electric solenoid or stuck valve. It is possible that recreating the wheel could be more time consuming, more expensive, and less efficient than fixing the problem.
I suggest using logic and reasoning to try to narrow down the problem.
Here is a link the the thread for my issue and how I dealt with it.
I have a 773G. Boom and bucket tilt were operating without issue. The other day I pressed the auxiliary hydraulics button and was messing with controls on joysticks. I plan to use the aux hydraulics in the near future. After messing with the controls, the boom and bucket will no longer operate...
www.skidsteerforum.com