It looks like the levels are unsolvable and impossible. I've tried them myself. These levels were made way long ago as far as maybe 2000 (I got the levels from the Garjen website) so I don't know if Cristóbal Márquez and Alfonso Celis are both active (chances of which are very unlikely). Their email is in the Garjen website though if you want to try contacting them, but I'm not sure if that even still works.
For packs that have different authors for each level like
this one and
this one, what should we do with them? Should we just create one NXP for each compilation pack? Also, in that link, Sculpture Maze already appears in one of Tumble Weed's packs, so I'm not even sure if we should leave that there. Training Course by Conway, I'm not sure if that appears in any other pack.
There may also be packs that have a mix of authors who are still active in the community, and authors who are no longer active. Assuming we are still under the rule that only packs whose authors have not been around for a long time are okay to convert, this can be problematic. For example,
this one has two levels by namida and Insane Steve. Insane Steve's appears in one of his packs. Out of the Frying Pan has already been used in Conway's pack, which leaves "Spider-Bytes" and "the union of two mates" by unknown authors. What should we do with the two levels by unknwon authors?
2. Should we also have Lemmini levels converted, especially since they also appear in the level database?
As far as I can see, most Lemmini levels are from Gronkling and grams88. Both are still active here, so this question is probably less important than one might expect.
There is at least one Lemmini author whose packs can be converted - Mariachi Skeletron Prime's. He's not active in the forum these days despite joining late 2014 (he didn't make an account for the new forum).
As a side note, looks like my
Scattered Levelpacks project really paid off.