How about trying to replicate the damaged cleat on a different piece of sheet, then once you get it perfect, cut out the old, weld in the new and blend it in. Try making a homade dimple die with a larger opening on the bottom to stretch it.
Actually, I've already begun welding up new cleats on the step plates, but if I had the right metal available (everything I had was too thin) I would have done precisely as you suggested. In fact, the homemade punch I made to reform the existing cleats would have been perfect for the task.
Speaking of welding up new cleats, I resumed working on them this evening and they are starting to look very nice. After I do a little more work to them I'll post some pictures.
Today I picked up a spool of welding wire and plan to resume working on the repairs very soon, possibly even tonight. I'll post some pictures later.
I love this new Forney .030" flux core welding wire I bought today, it welds so much better than the Lincoln stuff I was using previously.
Forney 42300 .030 Diameter 2-Pound Spool E71TGS Flux Core Mild Steel Wire - Amazon.com