The front wheels aren't locked? I'm not following here.
Once up on the ramps why would that matter? If I'm doing something that doesn't require the wheels to be off the ground and I'm only using the ramps, the parking brake is on. Yes, that's the rear wheels only but the front ain't going anywhere in this case.
If I need the wheels off the ground, I pull onto the ramps, set the parking brake, and then place my floor jack in position and raise the front end, then place the jack stands, and lower. I can now raise the rear and place the stands.
I don't see the risk here.