When the car is on the trailer, do you know how much weight the trailer tires are supporting? IF you do, do a simple calculation to see how far back the car would need to be moved to get your target tongue weight.

Or just put the ramps down and push the car back and measure the tongue weight. If it doesn't have to go back a ridiculous amount, just have the ramps lean back a bit, or remove the ramps and mount them on the opposite side similar to the bicycle.

I think that would be way easier than adding/moving axles.