As it says. One of the things that made the original Lemmings game so popular and fun was the ability to zoom in and out so the player can better focus in on the point-of-action when setting up actions. This was critical on some of the harder levels of the original, some had to be so precise it was down to the pixel (not saying much for those times, but you get the idea).
If that is not in the cards, then maybe just make it so fullscreen modes can be stretched across the entire available screen. The way SDL seems to do it (at least from my observations) is keep the desktop resolution and just "frame" the smaller resolutions in black and the larger resolutions (than the desktop res) go off-screen.
This would allow us to create more challenging level packs for players that would be doable for all ages. Even if it is just one or two fixed zoom levels that would be good, like 2x and 4x like the original (and Lemmings 2) had only one or two fixed zoom modes anyway, really all we need. Nothing real fancy. I say that but I am sure you are busy so if anyone else wants to write it and shoot it to me to help test I'd do it np.