I found this software http://knotter.mattbas.org/Knotter which is actually a really good starting point for the more regular knots. Where it appears to fall down is that the curves are not smoothed, so you can get a rough circle out of it, just not a smooth one, and getting to do complicated things with mixed weights sounds more difficult than drawing it myself. But it's very strong as a playground and as a place to sketch your design, from there bring it into illustrator or draw it by hand...
By taking the output and slicing it up into a tile and putting it into a mesh I was able to get what I was looking for.
(need a better bg tile obv)
...and I think I better just call it a win and stop right there. I don't want to get lost. To that end I've decided that every time I see the word "Gaelic", I'll shift a letter and internally read it as "Garlic." That should help things.