I've considered this problem for the bumper I'm making and plan to run a 1" wide x 1/4" thick x however long strip (haven't measured) from the side plate next to the upper bolts you see here:
and bolting it to the first hole you see in the frame behind the crumple zone you see here:
It will serve as a metal limiting strap. When pulled on, like under winch stress, it will be extremely strong (like one would expect of a strap) and prevent that thin plate from having to deal with all the strain. When pushed on, like a front end collision, it will just buckle (also like a strap) and allow the crumple zone to do its job. I got the idea off a 2nd gen ARB bumper I saw.
I plan on making that piece next time I'm in the shop. I'll put up some pics.