John knows a lot more about Bultacos than I do but I'm not sure I agree with that logic.
Every time the engine unloads - think engine braking- the thrust is reversed and as the motor creates a cyclic thrust so the basket will feel forces inward and outward. On a drag bike there should be zero reverse thrust so to speak, but after each gear change, the primary drive becomes loaded again causing a new thrust pulse.
Bottom line is that a GT750 and most other bikes from the era use hardened thrust washers without any issues. One difference though is that on a Suzuki the clutch shaft bearing is not retained in any way. It's just a roller bearing, so the basket will be subject to greater side loads than a Bultaco. On the GS and GT series, that isn't a problem because as John mentioned in an earlier port, the side thrust forces are not huge
BTW, how do you have enough space behind the clutch drum to weld on a plate/washer? On my bikes there is almost zero clearance between drum and basket. The drun sits hard up against the outer thrust washer and that's hard up against the drum. Does the drum but up against that step in the shaft, leaving some clearance?
Ask Ralf what he would do.
Good to hear that you are saving more weight. It all helps.