ok, I have absolutely no idea if this can even be done, but I figured I'd ask.
I want to create a new rabbithole. I know rabbitholes have been modded, re-textured etc. by other people far more knowledgeable and skilled than me, but I want to make a new one.
Reason being, I want to create a new career/opportunity/game level. Wouldn't it be interesting if sims could go to church/worship/have weird faiths? I got the idea from the Mummy's Curse opportunity in WA, could we just turn the statue thing into a 'normal' statue and all sims go to it to receive 'healing' (I'm envisioning the comforted moodlet being inserted or something) including cursed sims of course. Or maybe they go to prayer services/retreats a-la the concert/game function in a shrine. This is a massive idea. Maybe 'evil' sims who visit the shrine come out with the 'creeped out' moodlet while 'good' sims come out with the 'relaxed' moodlet.
I think I can figure out a priest/holy man/woman career.
I think I can figure out how to add the appropriate actions to the rabbithole. I just need the rabbithole.
Any ideas?

Any ideas about what? I have lots of ideas, but most them won't apply to what your talking about I'm sure.

Creating the rabbit holes is probably the easiest thing to do. Tutorials:TS3_Basic_HowTo_Mesh_Guide^wiki Moving to object creation as that does seem to be where your...question? lies, since you state you can figure out the actions and how to add them. It would be enormously helpful if you would actually ... ask a specific question. =P

so, if I simpl add intereactions as though it were a stove or something, I can add enough interactions to make it behave like the other rabbitholes?

There's more to it than that, I think.
There's a lot of layers to juggle on this one. Of course, you can do anything to it, as long as you know how to.

But first you need to know the concept on how new objects need to be made...let alone a new objects with interactions and pie menus that affect aspects of the game like Careers, Skills, Opportunities, etc.

Have you made an object mesh before?
Or played around with creating new interactions? Do you know how to?
Have you tuned any of the XMLs to create your own Tuning mod?
Having background knowledge in Programming Languages is also a plus, as you have to code your own interactions.

I've never made an object before...I have cloned successfully though, I think.
I've never CREATED interactions...but I have fudged them with the XML values of what they do.
I haven't actually created a tuning mod suitable for upload or anything, but I have 'tested' several of my own packages that do little things just to make sure I can change things. But I've only screwed around with moodlet values and suchlikes.
er...I'm quite decent with PHP? I think I can learn others in theory.

Modding for TS3 isn't done in php, it's done in C#. Programming for web is far different than programming for a game or application. You will want to take a look at the tutorial by kolipoki on adding interactions to objects.

so I think I can follow his tutorial pretty easily...but I'm having issues locating the file that has rabbithole interaction. ok I found the one that says rabbithole zoning that just makes the camera move when a sim is in the rabbithole....but is that really all that makes a rabbithole a rabbithole?! in S3PE the files for 'hospital' 'restaurant' etc only have things specific to those rabbitholes...ie the hospital has the 'have baby at hospital' interaction tuning and whatnot. sooooo I'm having issues figuring out exactly what functionality makes a rabbithole...a rabbithole. if that makes any sense