Do you still have this conversion with the non-working mod? If you do, could you send it to me so I can determine the problem?
You say that the lemming ignore most of the terrain in the Sega styles. Does this happen only when trying to load the style as part of a mod, or does it also happen if the style is loaded from the main styles folder? In either case, I'm guessing the problem is somehow caused by the styles not having separate terrain masks, but that shouldn't cause any problems if the style names are different from those of the ones included with SuperLemmini.