Unfortunately I don't have any i-Products, but the few screenshots posted do look cool.
Like the style of graphics.
I expect you'll definitely want to get feedback from i-Players on their opinions of the controls. There aren't too many ports of lemmings that are strictly touch-only. I do see that you've already taken care to make the main characters fairly large in size compared with the relative sizing of lemmings, which is definitely a wise choice for touch.
The sky is the limit when it comes to extending the gameplay beyond what's available in original Lemmings. Examples to think about:
- new skills (this is obvious, and is what happened with Lemmings 2 for example. But be careful not to have too many skills available at once in any level, as it's unlikely there's a good touch-based way to select amongst too many skill choices)
- pick-ups (get extra skills, extra characters, speed changes, etc. etc. etc.)
- more advanced contraptions (eg. teleports, moving land, slingshots, gravity changers, size changers, etc.)
- new "land types". In Lemmings it's basically regular land (destructible) and steel (indestructible) [okay, there are also "one-way" walls]. Water/lava/acid are deadly. Given that your main characters are turtles, there should definitely be some swimming-like behavior for water, for example:
* they will automaticlaly swim on the water's surface (if the water's deep enough), during which time they can't perform certain regular skills they could perform on solid ground (eg. digging no, but exploding yes)
* some of the water can go up and down (like tides) which can influence where the turtles end up (because they float with the changing water level, and can even transition between on land and on water if the water level falls below some piece of land)
* etc.
other things to think about include slippery ice, sinking quicksand, etc. Acid/lava can be used for types of liquid that kills.
Interesting you mention the level editor is Flash. That would mean level editing can't be done on i-Devices. Might want to keep that in mind.