I would be very careful about making medical claims about cannabis preparations. If you are marketing a "cure" you have to go through the entire FDA process with clinical trials that can cost around $500 million dollars and take a decade to complete.
http://www.medscape.com/viewarticle/405869_4 Add to that the fact that cannabis is still listed as Schedule 1 which can not currently be researched according to the FDA and you will begin to see what an uphill battle this is.
My advice to you is to pick a State that you want to call home to your company. Find one where the laws are friendly to cannabis. Obtain the appropriate licenses. Then develop a preparation that you believe will be beneficial. Get it to market so that you can start realizing revenue. You can call it "Foot Magic" or something along those lines. Again, make no medical claims.
You can begin to find people (with a doctor's recommendation in a medical only state) that have the condition that you would like to focus on and work with them to begin to study the outcomes. You can then begin to dial in your recipe. When a change in federal scheduling occurs, you will be better suited to take any next steps. You can also make relationships with Doctors that work with diabetics to make them aware of your work.
Of course this is a vast over-simplification of a very complex process. I would definitely not try to go it alone in forming a start up in the cannabis field. Find your self a good team to help you through the process. I would hire a good consultant that has experience in the industry to help you out.