The biggest hurdle on supporting SML3 has been completed; auto tile-set (and sprite) changing.
SML3 added that each level can have multiple tile-sets that change when you go through doorways, to support this I added that it simulates playing the level and figures out where you can go, then changes the tile-sets accordingly. It works almost perfectly!
I haven't yet got it changing the sprites too, although I have the data.
the colours are different paths being traced in debug mode.