I think LWC has just about covered it

...That's a very nice 2 man set up by the way LWC
The main thing you need to think about is -
THE WEAKEST POINTYou could have the strongest ratchet straps in the world but if the anchor points are only meant to carry light loads or meant to stop slight movement of the load while in transit...then this will cause you some serious problems if you have an accident.
Again, if the ratchet straps were worn or not correctly positioned (forcing the load onto one strap as apposed to equally over several) then this could cause it to fail (overloaded strap).
Bolting the system down (by far the BEST solution in my humble opinion) also has its drawbacks - you need to calculate the weight/velocity/energy to accurately gauge the type of bolts/plates to use and where best to position them.
A good engineer will be able to do these calculations and work out the optimum positioning with ease

Always think -
WEAKEST POINT