I missed the question earlier.. sorry about that..
I've never heard of someone doing this BUT, it sounds very similar to just using large/long spring perches.
The issue though, the overload (normally) is still bent like a spring. That means it will act like a spring just like it did when it was still in the spring pack.
At one time, we did have "flat" overload springs on our X. They came with the OME spring pack (I think that is where I got them). They didn't limit the suspension movement unless the springs went inverted. They did hang up on rocks which is why I removed them. I can't see how welding them to the spring perch would help any more than just having them in the spring pack.
Also, remember, jeeps are SOA by default, as are ranger. Explorer are SUA which is why they don't usually get the bad axle wrap. That is until you go SOA.
Personally, we don't run an overload spring anymore now that our X is more of a wheeling rig. The overload was limiting upward suspension movement. Of course, our springs will invert when we really flex the suspension which isn't exactly good for the springs.
truckhaven-rti-2011-1 by
maniak_az, on Flickr
~Mark
edit:
It just occurred to me. . If you were to use a flat overload, and reinforce it so it wasn't just flat spring steel and weld that to the axle and make it part of the perch, I could see that helping more than just welding it flat on there.
something like this, but longer..