1. Put in Ella's world by simply backing up the original EA .world file for IP in its game bin folder in program first and then overwrite that file with Ella's. And/or at least add NRaas Overwatch (and ErrorTrap) mods.
2. I tweak the world by deleting the resort towers at the resorts and leaving that space open in case I want to play one as a resort later. They are now community lots. (Delete concession stands and buffets to avoid problems.)
3. I move everyone out of the houseboats and into homes on land. And, then I delete all houseboats, except for the ones on the problem ports (Primavera & Premium), which I make NVA along with Port Pleasant where I add a boat.
4. I evict the Ichtacas from the castle and deny access to the very top floors, moving the bedrooms down one floor, deleting the upper outside stairs and stacked spiral stairs, and deleting the arch in front of the front door.
Ichtaca Castle - had two full flights of stairs before getting to arched door:
Added basement, moved top bedrooms and kitchen down one level, etc.
http://lvlt.thesims3.com/sims3_asset/sims3_asset/thumb/shard000/000/086/208/97/roof_up_original.jpg
http://www.thesims3.com/assetDetail.html?assetId=8620897
5. I evict the Collins to delete the top floor, front arches, and wall between the front porch and living room.
6. I evict the Vidals to expand that house so there are no outside stairs.
Petite Painted Lady - had outside stairs to the upper level through a bedroom:
Now has spiral stairs leading to upper hallway and a roomy driveway.
http://www.thesims3.com/assetDetail.html?assetId=8620818
7. I evict the Hamadas to delete their front arch and columns and I move the fences out one tile on each side.
8. I flatten the ground around the fountain and delete the stairs in the center plaza.
9. I move the children's section down to ground level in the library and add a children's bookcase and end tables.
10. I replace the Modern Marvel and Modern Folly lots with those in my studio. And I'll do the same with the Solitude lot for the Loner soon. (I may upload other lots I've redone if there is an interest.)
Overwatch cleans up vehicles and stuck sims at 3am every day (unless you set to do some other time). The first day my clock stopped at 3 a.m. for awhile as it went through everything. The second day there was no lag at 3 a.m. My logs report that buffets and concession stands were the culprits.
Yes, it's a lot of little tweaks; but not something you can't do. You can play without any mods or Ella's fix as well, but with pets, some will get stuck. And the game will spend a lot of resources trying to route them. So, you'll have to find them and reset them and then block that spot with a big rock or other objects.