Why is my vault's bevel unevenly applied?

Question

I don't quite get what's going on. I tried everything: applied rotation, scale, tried re-making the geometry, and nothing works. Could it be that a slight misplacement of a vertex causes such a dramatic change in bevel? It makes no sense. This was created from being mirrored, but it won't apply right. I tried all modes, which I will show below. There is only one that works, but since it doesn't apply it evenly to the bottom portion, I cannot use it as it destroys the top. I need this in order to get the profiling right (otherwise it shows an ugly, impartial application which I demonstrate below as well).

Here are the different types of modes of bevel that I tried (note that they're exaggerated to show how they are unevenly applied).

Offset (note the twisting of one side and another side's disproportionate look):

Width (it looks OK, but it's not when the bevel is applied in excess because it shows that not everything is scaling in the same amount):

Depth (really weird--should not be such a dramatic difference!):

Percent (this is the only one that works relatively better, but it applies most heavily at top, whereas I need it to be applied to the bottom evenly, too):

Here's the reason for why I need the bevel:

Here's what happens when bevel is applied: Any advice is greatly appreciated!

Note that the file is found here:

Answer 1

How do you get to Killarney? Well, sir, I wouldn't start from here if I were you....

Just teasing.. I think some of this may have been be easier if executed before the array was applied. (Making an array out of arch-peak-to-arch-peak sections may still speed things up when adding detail?) This is a fix, rather than a solution, I'd like to know why the Bevel works the way it does.. whether the algorithm could be improved.

1. Make a copy of your existing path-curves (you can CtrlJ join them into one curve object to save time later) call it, say 'Miter Path'
2. Make a copy of your existing profile curve, and delete all but its flat base .. 'Molding Base'
3. Use the Molding Base as a the Bevel Object for your Miter Path. You now have a set of ribbons
4. With the ribbons anywhere you like in Z, select them, and then the Vault object. Put the (active) Vault into Edit Mode
5. From an orthogonal view down Z, hit 'Knife Project' in the Tool region. This will cut a set of edges into the vault where you would have liked the bevels to be.
6. There will be some extraneous vertices.. there are various ways of tidying them up .. I selected one of them , then used Select > Similar > Number of Connecting Edges to find the rest, and then X > Limited Dissolve to get rid of them.
7. I also selected the penultimate vertices around the pole of the vault in order, hit J to make a ring of edges, and deleted the faces at the pole, assuming there will be some kind of boss or rosette there in the end.
8. Now you can delete the faces between the knife-projected edges and CtrlE > Bridge Edge loops creating the flat bevel to accommodate the molding. CtrlR cut a loop down the middle of each bevel.
9. ShiftD Duplicate the central loops of the bevel, P separate to a new object, and AltC convert to a curve - U resolution 1 - this will be your new path for the molding profile
10. Move the origin of your molding profile to the center of its base - (this point will lie on the path). Use the molding profile as the Bevel Object for your new Molding Path. You may need to rotate it in Z in Edit Mode to get the molding to face the right way.

I apologize for the lack of step-by step illustrations - everything important is done by step 5.

Alterations on Layer 11.