Probably OK but any modification voids warranty and changes the geometry, which changes the tested strength. The DIY welding is also subject to failure.
I would consider:...... NOT adding height. Not doing any welding. Adding "outrigger" support by bolting. Not changing the wheel design in any way.
I actually would consider rolling over, on the floor, in some fashion, as Carl says. This method could cause sheet metal damage and may need a few inside the cab supports to maintain anti racking.
I do not know the reason for you wanting a rotisserie.
I have seen Asian VW bus restorers use a large steel loop fastened to each end/near each end of the vehicle. They just roll it over.
Made from rectangular tubing. 6-10 sided. Hexagon, octagon, decagon or round.
