I wouldn't drive anything from one side personally no matter what the machine is. Out of interest have you seen it done somewhere?

For plasma cutting forces are not there and as long as bearings under gantry have a fair spacing I don't see that it would rack in that sense (bind up)

But inertia forces are there. So rapid changes of direction on the gantry would start to give a bit of lag on the non driven side which means slight out of position cut. Question is whether this error would be large compared to kerf - someone who has used plasma more recently than me may be able to answer that one.

I would slave both sides or drive both sides direct.