Let me first say the combo Phil put together looks great. Secondly, I am an avid bow tie wearer with saxon attire and will second the plug for Beau Ties Ltd.
Thirdly, I think sartorially there would be nothing wrong with wearing a patterned or solid "day" bow tie with a kilt. Many of us wear an "evening" bow tie with a kilt and don't think anything of it, in fact the evening is the domain of the bow tie. In reality "white tie" "black tie" on an invite isn't referring to a four-in-hand.

Finally, however, and this may be just me. There is something about a bow tie with day or casual kilted look that just doesn't work for me. There is a picture I have of the Duke of Windsor wearing a bow tie with "Morning Dress" and it is very much the same for me. I cannot explain what it is and I won't even try.

If it is something you want to do, go for it. Phil shows that it can be done with style.