To start with getting a trucks rear wheels to climb ramps will be tricky pulling a trailer(open diff wont help). Second when the tractor gets on the trailer it the only wheels that hold in park or with parking brake are trucks rear wheels unless its in fwd even with trailer tire blocked it will move some and will still take weight off the truck tires. And when it does move it will fall of one ramp then is when the fun begins.
Not wanting to disagree but I have done wrong enoght that my pucker factor just got really high when i read your idea not that it won't.
Find a ditch theres always one within 1/4 mile, a short drive and asafe way to load or unload.
It wasn't my idea, it was someone elses but it sounded o.k. to me.
My truck will climb my steel ramps all day long without a problem. Pulling an empty trailer won't make any difference.
If I was doing this I would back up on them to make getting them under the truck and the truck off the ramps easy.
If the rear of the trailer is blocked so it can't go down by the bottom of the ramps or additional blocking I don't know how it will take any weight off the truck since it won't be able to lift the front of the trailer up. We aren't talking about blocking the wheels we are talking about the blocking that is built into the ramps to stop the trailer from dropping, or additional blocking as required at the rear of the trailer.
I fail to see how anything could move under these conditions.
I have used my portable steel ramps many times in the last 20 or 30 years and I have never put myself in a position that I had a problem.
A ditch is a good idea but the poster wants to be able to load and unload where he needs to not where it is possible by natural terrain. The ramps are the equivilant of having a portable ditch. Also if he only has a 2 wheel drive pick up there is no way he is going to pull 8,000 lbs out of a ditch, yet going down hill on the ramp will not be a problem.
I still think the use of ramps is a good and economical idea. Please convince me otherwise.
I think you didn't catch the part of blocking the rear of the trailer. If only the wheels were blocked you are right it could unload the rear wheels of the truck.
If it was my truck it is so friggin heavy it wouldn't make any difference, but that is not what we are talking about. By blocking the rear end of the trailer it makes it fool proof. The man has a 6K# tractor and a 10K# trailer. I think he is good to go.
I don't think loading a tractor under these circumstances would generate much U-tube interest. You just drive it up the hill, tie it down, drive off the ramps, throw the ramps in the back of the truck and have a great day.
That has been my experience........

If I am missing some other hazzard please explain.