Here is a new scriptclass you can use for making non-spiral stairs using the spiral stairs as a base to clone from.  What it does is eliminates the walking up stairs in a spiral animation, and replaces it with a direct teleportation from the entrance routing slot to the exit routing slot.  For purists who need to see correct animations this will be disappointing, but for builder players whose main interest is to get the building looking as they want it, and still allow the sims to move around it freely, this could be exactly what you want.

Suitable for half or quarter landing stairs, winding stairs, ladders, ramps, and stealth portals.  All heights - all inclines.

Instructions (some experience with object creation required, can be done in TSRW or s3oc/pe):
1) Unzip and import the attached S3SA resource to your cloned stairs - it must not be renumbered at any stage, since the IID is based on the class name.
2) Change the Scriptclass entry in the OBJK to say "Sims3.Gameplay.IngeJones.ijSims3Stairs_Snap"
3) Edit the mesh and textures to suit the appearance you require.
4) Edit the footprints as required.
5) Move the routing slots to the new landing positions, rotating also if necessary so that the sim begins and ends facing the right way.   It doesn't actually affect use if the rotation is wrong, but the location needs to be correct or you could end up with a sim trapped in the middle of the stairs.

Please post if you notice anything wrong or missing from these instructions.