Oh yeah, I actually finished modding those Steffi Love boots. Originally they were fake flats, but I sliced off the soles, hollowed them out to make room for föat feet, then glued them back together. They still only fit articulated Steffi's feet, but at least the proportions don't look as weird.
All hollowed out and ready for reassembling! I just used whatever glue I happened to have laying around.
The seam split when I rammed her foot down in the boot too carelessly. Oh well, just pour some extra on.
Steffi Love's articulated feet aren't pretty, but they do the trick.