That's a smart design! If you spin up to 0.5g and accelerate at 0.5g (which, while not enough for takeoff, is plenty for interplanetary travel) the tether angle

That's a smart design! If you spin up to 0.5g and accelerate at 0.5g (which, while not enough for takeoff, is plenty for interplanetary travel) the tether angle would be 45 degrees, more than enough to get out of the exhaust plume. Another free benefit would be that on a change of acceleration, angular momentum would be conserved. Rotation would increase or decrease to keep the acceleration felt by the occupants approximately constant!