Onslaught of Tipping equation?

If you know where the center of mass is for the whole pallet-object system, then you can figure out the maximum angle of tippage beyond which it'll topple. If a vertical line through the center of mass intersects the pallet (stays within the pallet's base-width), then it's stable.

The question is too generic to come up with a meaningful equation. You have to know the forces that the object will encounter during it's travels.

Generally, tipping occurs when the center of gravity of an object moves past the vertical line over the pivot point. You're on the right track with the wide pallet, that moves the pivot point further away from the center of gravity. Another risk reduction measure you could take would be to effectively move the center of gravity lower in the assembly by packing very heavy things around the base, on the pallet, if there's room. The more you move the center of gravity lower, the higher the tipping angle will have to be for the assembly to go over.

Something tips when the line of applied acceleration drawn through its CG falls outside the convex polygon formed by connecting its outer support points (e.g., by running a string around them).

The applied acceleration is, of course, g along the vertical, plus any acceleration along the horizontal ah. Thus you'd have to know the maximum ah value, which includes simple forward/aft acceleration as well as lateral acceleration such as that due to unbanked curves, ship rolling, etc. If h is the height of the CG, and x is the horizontal distance from the CG projection to the nearest side of the pallet, basic geometry says that the object and pallet will tip if ah/g > x/h. And if tilting is involved the situation gets more complicated and (needless to say) worse, since this may reduce the value of x.

I believe that some shippers allow the option of having the pallet anchored to the floor. This is worth looking into.