I now have a PL2 (or any stock paletted terrain) CM11\DATE folder setup for matched sky color and terrain seasonal variants.
Must use CM11 "Copy files based on date" and "open"ing of Campaign with CM11.
Can also be used for JWP and WFP by putting this DATE folder in such as "CM11\Patches\PL2mod\DATE" or directly in a terrain folder beside 3DPatch folder such as "CM11\Patches\PL2PL\3DPatch" + "DATE".
Yep, CM11 searches "patches in use" for DATE folders and applies the files with the added advantage that these files are removed from the main DATE folder and Simpatch when removing the patch.
I also have a NML replacement tile set for greater visibility of NML objects.
PM me if you're interested.