Add an L shaped pivot arm (I'll call it a Trigger Bar) to the lock plate to push horizontally on the arm of the Sear with the vertical arm of the Trigger Bar..
It's lower arm of the L shape comes out and across the top of the trigger plate underneath the trigger blade.
The pivot position for the L shaped of the Trigger Bar can be a stud installed on the back side of the plate just below the Sear arm. Slotted to accept the width Trigger Bar and the Bar pinned in place so it can pivot against the Sear Arm when pushed upwards by the Trigger Blade.
The Trigger can be either a Single Trigger, or if positioned correctly a DST.
Either would push the Trigger Bar upwards and release the Sear by transfering the motion though it's pivot and push the Sear Arm directly in towards the LockPlate.
I think the Sear Arm could be reshaped , the Sear Arm Spur deffinetly removed as it is not needed.
The portion that the Trigger Bar is going to press against to release the Sear can be reshaped as needed for better geometry and leverage.
I think it'll work,,The same idea does on a Luger.