Nepster made a topic about updrafts once, with a quiz. Have the updraft rules been simplified since?
A change was made so that instead of reducing the "distance fallen", it just sets it to zero - essentially, all fall above the updraft is just ignored.
Let's take a look at which Lemmings Plus levels would be affected by removing direct drop, and how hard it would be to work around this. Note that I'm only paying attention to levels where the intended solution breaks (even if other solutions exist, but I will mention if they do), not simply ones where challenge solutions break. I have also specifically pointed out where affected levels are Sky levels; if special handling for this is implemented, no change is needed (I'm thinking something along the lines of having a seperate type of exit that *does* allow dropping in; graphic set designers would then be expected to give visual cues to the difference). I also haven't listed cases where it only affects the talisman solutions, not the main ones.
My prediction before looking through: Most of the affected levels will be in the Sky set. There may be a couple of other affected levels, but not many.
Now, let's actually look.
Medi 7 "Leap of Faith"
http://www.neolemmix.com/old/levelimg/lpi/0307.png>> The direct drop is not an important part of the level. Simply reducing the fall distance would solve the problem here.
Danger 1 "Inside Outside"
http://www.neolemmix.com/old/levelimg/lpi/0401.png>> If I remember correctly, a solution that does not use direct drop exists. Before making any changes, I'll try and see if I can reproduce that solution, and if so, make it the intended one.
Psycho 6 "The Bulldozer"
http://www.neolemmix.com/old/levelimg/lpi/0506.png>> This could probably be fixed by placing terrain below the exits, and an updraft above the exit trigger areas.
Genius 20 "Cactus Central"
http://www.neolemmix.com/old/levelimg/lpii/0520.png>> This one can probably be fixed with updrafts, but it would definitely make the solution more obvious.
None from Lemmings Plus II Bonus Pack
Timid 11 "A Digger Would Be Handy"
http://www.neolemmix.com/old/levelimg/lpiii/0111.png>> Could be fixed with terrain and updrafts. Is a Sky level.
Timid 14 "Some Say It Was A Lemming"
http://www.neolemmix.com/old/levelimg/lpiii/0114.png>> Same as Timid 11.
Timid 16 "Heads In The Sky"
http://www.neolemmix.com/old/levelimg/lpiii/0116.png>> Same as Timid 11 and 14; also, solutions that do not involve direct drop exist.
Fierce 5 "In The Frenz-zone"
http://www.neolemmix.com/old/levelimg/lpiii/0405.png>> Removing direct drop would not make this level impossible, just increase the accuracy required for building to the exit. It must be kept in mind that it is a Frenzy level, though. It's also another Sky level.
Fierce 9 "The Troll Level"
http://www.neolemmix.com/old/levelimg/lpiii/0409.png>> Same as Fierce 5, except not a Frenzy level.
Teamwork 7 "Turbulent Affairs"
http://www.neolemmix.com/old/levelimg/lpiiibonus/0407.png>> Terrain + (maybe) updraft solution works, is also another Sky level.
Secret 3 "The Lazy Streak"
http://www.neolemmix.com/old/levelimg/lpiiibonus/0603.png>> Adding terrain below the exit would work (no updraft needed). Is another sky level.
None from Lemmings Plus IV
Puzzling 3 "Horizontal Access"
http://www.neolemmix.com/old/levelimg/lpo/0203.png>> Doesn't break the level, just increases the precision needed. Is a sky level.
Puzzling 27 "Inversion Therapy"
http://www.neolemmix.com/old/levelimg/lpo/0227.png>> Has alternate solutions that do not involve direct drop.
Perplexing 20 "Current Affairs"
http://www.neolemmix.com/old/levelimg/lpo/0320.png>> Will only need changes if floaters/gliders are prohibited from exiting in midair too. Is a Sky level.
Mental 18 "...wait, what?"
http://www.neolemmix.com/old/levelimg/lpo/0418.png>> It's possible a direct-drop free solution exists. If not, a new solution would be needed, unless the level is changed to remove its signature upside down exit. Note that this is a repeat of Puzzling 27.
Mental 28 "The Troublesome Trio"
http://www.neolemmix.com/old/levelimg/lpo/0428.png>> Could be fixed by moving the exit upwards or placing terrain below it. Is a sky level.
Playtime 1 "Quarantined Threat"
http://www.neolemmix.com/old/levelimg/lpo/0501.png>> Could be fixed by adding terrain below the exit, is a Sky level.
Playtime 7 "Glider Frenzy"
http://www.neolemmix.com/old/levelimg/lpo/0507.png>> If floaters/gliders aren't exempt from changes, then the precision needed for this level will increase (do note that it's a frenzy level), but it will not be rendered impossible.
None from Holiday Lemmings Plus.