i've been doing a lot of lunges recently because i find that squatting kills my BJJ training, but i can lunge and still train regularly. this is mainly because squatting seems to tax my adductors too much.
i tried step ups but i feel like if you try to raise the weight up, you automatically kick off the back leg.
stepping backward lunge seems to be more applicable to squatting because the leg with the knee bend takes more of the load.
with weighted pistols i've been using a zercher grip. seems to make everything more natural.
for fun, i've been messing around with this type stuff recently