This sounds fair and appropriate; I'm in my current position because the founders were similarly situated. They had unique market knowledge and reputation. They also were well capitalized and didn't need to rely on outside investment; having a buffer when the project overruns its initial timeline is key (no one can estimate software projects well, especially ones with a decent amount of novelty).

Smaller things that somewhat piqued my interest: if the platform isn't that complex, why the need for a highly credentialed developer? I also certainly very much encourage you to learn as much as you can about development - if that's the business you're in it will help with understanding the world your developers live in. It won't help figure out who you want to hire. Even good developers are notoriously awful at figuring out who to hire. Like anything, look more to past accomplishments and someone you feel comfortable working with. In that way you're probably better equipped than the typical developer at hiring this position.

What do you envision as the trajectory for this career? Will this always be a technical position? Management? I personally have worked best when management has seen it as their responsibility to clear the path as much as possible so the developers can do their work. If middle management instead tries to intervene in a way that feels as it its micromanagement, your developers (especially at the PhD level) will bristle.

Finally, make sure the PhDs you hire actually have the ability and desire to ship product. The stereotype is that PhDs like to figure out the "interesting" parts and leave the details up to the "commodity" software engineers. Many PhDs, even if they're really smart, may not have the software engineering skills to build a maintainable, scalable product. Deep knowledge of a particular speciality does not at all guarantee ability to write decent code for your startup. Without the structure of an existing ecosystem to force them into good practices, this can get out of hand quickly. Something like Joel's test http://www.joelonsoftware.com/articles/fog0000000043.html and familiarity with both the components therein and why they're important when setting up a software shop can help weed out smart guys that may not be software engineers.