That mode was equivalent to using angle mode and incrementing the target the way velocity_openloop does it. So you can still do the same thing manually, but in your case it doesn’t sound like you need the incrementing behavior. Just set target angle directly.
You could try angle_nocascade. I use it on my CNC machine in voltage control mode for fastest possible response, since the maximum speed is not high enough to need current control. Your high resistance motor is probably the same way. It needs much higher PID gains than regular angle mode. I use P_angle.P=75, I=10000, D=0
An experimental feature you could try is deadtime compensation. It improves linearity of response at low voltage, and greatly smooths out open loop motion, which is normally sort of steppy. It’s not perfect though, and usually results in a sort of “tick” at each zero crossing in open loop which you can feel if holding the motor in your hand or hear if it’s sitting on cardboard or something that can amplify it.