i trip over 3mm plate evreyday at work but i wouldn't piss on it if it was a footpeg.
stick with the stainless.
all that hole drilling made me dizzy ji.
i just bend some 3mm stainless around a bit of pipe in the vice then after i've welded it to the origional footpeg i nick some grooves in it with the good old angle grinder.
i don't like the idea of drilling holes in stainless let alone that many.
if you do drill S.S. then a slow drill speed is optimal.
i weld mine with the MIG using 309 wire.