your basis for stating what you have is? You have obviously checked out the
ground conditions and got the calculations on hand to confirm this type of
build at 10' high plus foundation havnt you?. I have to say what you have
suggested is seriously dangerous. You may be right but if the original
poster is correct with his height then I think you are wrong to suggest
anything except get a structural engineer in to specify. He may only park a
car there but when a visitor arrives and the wall collapses on someone then
you obviously will stand up and say "I told him what to do" Please note it
is not only dangerous to have a structure like this but also to try to build
it. A 10' high wall of ground could be seriously unstable in itself.