As a hobbyist games programmer myself, and having noticed which mods tend to work from the base game path and which need to be in the WA path, I'm going to (tentatively) suggest that EAxis has made the loading of code and data inheritance-based, like so:

  1. Load base code/data from original TS3 path;
  2. Load updated code/data from WA path (where WA data differs/is newer)

This means that code/data from BOTH the base and WA paths is loaded, but code/data from the WA path will override the base in the same way that mods do. This means that any mods in the base path are at risk of being overridden by WA code/data, which is why some work and some don't - the ones that don't work from base are those for which WA has updated code/data of it's own.

NOTE: This produces the side-effect that any mods that don't work from the base path MUST be updated to work with WA, because WA itself makes changes to the same part(s) of the base game the mod changes, and is therefore also overriding the mod!

As far as adding mods to a WA-enabled game, the only way to guarantee that a mod will take precedence over all is to run the game - and all mods - from the WA path and ignore the base TS3 path entirely from now on. The easiest way to think of it is this: WA is itself nothing more than a very sophisticated (and dare I say it, bloated) CORE mod for TS3, created by EAxis rather than by the gaming community. Therefore, if we want to change a WA-enabled game, we have to override both TS3 and WA as a whole.

Perhaps we should just defer to the original Rabbithole system: the Sims (preferably including one female child in a blue-and-white dress, for continuity's sake) could chase a White Rabbit (bearing a pocket watch and complaining about being hopelessly late) down a seemingly neverending hole; they could all have tea with a madman, a raving hare and a sleepy dormouse with a penchant for teapots; meet a crazy cat whom they cannot fathom that has a tendency to appear and disappear at random; watch two overweight, badly-dressed men bonk each other over the head repeatedly while singing a bunch of nonsense; chat with a clearly stoned caterpillar about nothing in particular, then launch their own search for magic mushrooms before finally waking up and entering the school...

At least, that's probably how EA's version works, which is why it takes so long. 

Possibly not. Essentially (as far as I can tell) it was simply a patch that pacths the patch that was supposed to have fixed a hundred things that are still not fixed but EAxis say are. (If that makes any sense - probably as much as EAxis, so all good.  )

I wasn't one of the people for whom the patch had to be made, but now all of my 1.3 savegames make 1.4 crash, so as per usual, what's a new-and-improved bug-fix for some is a new-and-improved bug-fest for others. Highly annoying to have to restart my legacy game because EAxis rotated theirs the wrong way again.