First of all, I am very flattered that you like my world, and very glad that my research has been helpful - as that was part of the reason for this thread.
The businesses - I needed the world to have enough for purchasing for dynasties.
For the hill with the civic centre, I created it using the 'hill' tool in CAW, but I'm seriously considering taking the map into photoshop to fix it up, because I keep getting irregularities around the road.
The dark rock colour I used was from one of the other EA worlds... I can't remember which at the moment, but I'll find it later today when I open it. Most of the textures I have used come from Hidden Springs. All of the textures on that link are from EA worlds, and if used in the right combination, work well. If you find a texture looks to repetitive, like the shale, you can always edit it and replace it with another to see how it looks. It's also possible to extract the terrain paints from in-game for use in CAW, if you have S3PE. Just remember to limit it to 8 textures per chunk in the final version, and, to use S3PE to delete any unused textures before exporting.
The rabbitholes in basements wouldn't be an extreme issue IF you have the lot big enough for the rabbithole. If you let it hang over the edge it becomes a problem, with sims exiting rabbitholes into nothingness. If you're not against custom content, MTS have a set of rabbitholes that use a rug rather than a building. That way you can build the rabbithole how you like, and just place the rug on the floor.
As far as research went, I started thinking about what I wanted - an efficient world that will hopefully meet challenge requirements when it is finished. I've played extensively throughout the year in the challenge tournament, and also made a few attempts at a dynasty (I'm great at starting, and starting over, and over...). For each step of the way I have compared different EA worlds. It helps to have S3PE and CAW to open the EA worlds and see how many spawners and where. In S3PE you can see the _XML files for the spawners and get an idea of which spawners have what. Plus some simple play-testing - having a sim with level 10 fishing skill check the spawners; placing the butterfly spawners in clearly marked grids on a lot to work out which one is what in the code (they are named differently) so I could work out what spawners to place... The list goes on. For each step of the way I google what I want to know, or play-test.
I think a couple of pages ago I wrote down what spawners I would use, but it depends on what you consider 'minimum'. There's a working minimum - I've used that for fish (since there are always fish you don't have to worry about spawn rates), gems and metals and insects. Spacerocks... I may just add another 'small' spawner as it doesn't seem to spawn often enough, but we'll see how we go when I get hold of an alien. And seeds, you could actually get away with just one spawner - the 'special 1' spawner, as it has a 25% chance to spawn each type of seed. However, each of the spawners have different quality seeds. I have included:
1x common 1 (for the chance to get a poor quality apple seed for the 'bad apples' opportunity)
1x common 4
1x uncommon 3
1x rare 3
3x special 3
During play testing it seems that 1 common4 may not be enough, so I may add one more.
For play testing I have been practising some of the challenges, but for routing the only one I used was Overwatch. Errortrap can be use before you export your world (and before you add the population) to clean up certain items the game leaves lying around making the file big. Using mods like that is a new step for me, and I haven't found anything else to use, though I have seen somewhere where they use a mod that speeds up story progression significantly, and pushes story progression much further than the game does, to test for multi-generational glitches that tend to appear much further down the line in a game.
