I'm no expert on this, I'm only making (what I think are reasonable) suggestions, so please go ahead and do what you think reasonable.

I'd just suggest having a bit of a flat top to the triangles instead of the thin point.

You could always look at it that if you fail, you haven't lost anything. If you get it to work, you have a playable 12-string.

You should only have to set the tensioning up once. You can always slacken the strings off to get tools in the soundhole. I often put tape round the strings or use a capo up by the nut to keep the strings on the tuners and then slacken the strings off so I can remove the saddle to work on the height.