Hi I'm Will from Scotland
I'm an Architect and have used Adobe Illustrator quite a bit over the years for doing architectural illustrations. We can't justify the expense of renting Illustrator/Indesign/Photoshop for occasional use; we are desperate for a serious replacement for Adobe CS and it looks like you might be on to something here.
By the way, in architecture school, we do a lot of intensive illustration work. You might consider giving away free copies to students. A lot of practices license Adobe CS because students who figured out how to use it at Uni have persuaded them its required to do good illustration / colour reports / rendering post production etc. If you can go in and get them hooked on your products instead, they will then go on to demand that practices buy it when they get a job. I noticed that some of the developers are based in Nottingham, UK. It's worth having a look at the degree shows at the top schools like the the Bartlett School of Architecture and the Royal College of Art to see how your software might be used in this industry.
All the best,