I tried rerunning the challenges after the mods came out and there was just not much interest. Feel free to play with or without mods and let us know what you wind up doing!
Most of the challenges were great fun and generated some very creative and skillful entries. At least for me, some of them really were challenges.
(1) I wasn't so interested in re-doing challenges I'd already done--and the "Most Beautiful" challenge which was underway when the mods started coming was thoroughly won by @wasabi333
), who may not even have seen his settlement as an entry.
(2) Once mods are out there, I think (and this is my opinion only) that any challenge would need to have a list of permissible or, in some cases, required mods to make an even playing field. I can foresee a long discussion leading to such a decision.