Basically, no this wouldn't work because your transmission is already setup for a lockup TC. This would just be adding parts you already have and not what you need. If you want your TC to lockup, you need to have a lockup TC. Replacement with the correct TC is going to be your only way forward.
Just removing a gear will not change the torque rating. It will change how the engine power is delivered to the road.
The rating is based on the strength of the case, the design of the teeth etc. If you exceed the torque limit then gears can be stripped or cases split or burst so when tuning engines that gearbox torque limit should be checked.