A good designer is a good designer. If someone holds back the company later, that's not good design.
Design is way way more than logo and paint. Interaction design is just plain being able to make stuff that works well for people -- that's the kind of design I'm talking about. Should have made that more clear.
It looks like you are the "designer" on your team. It also looks like you have an amazing background in software development, program management and entrepreneurship. That's the kind of designer you want as a cofounder ;)
As you say, design is a lot more than some paint and a logo. Interaction design, information architecture... are all VERY important at the early stages. I do think the early devs should have this as a skillset though (much as you do) opposed to cofounding with a straight up interaction designer (no matter how good they are).
Given the amount of equity a cofounder gets it I would tend to look for people who could be 100% utilized (working all the time to get the company up and running). It can be hard to keep a full time designer busy unless you have a team of devs pumping stuff out for them to craft.
Design is way way more than logo and paint. Interaction design is just plain being able to make stuff that works well for people -- that's the kind of design I'm talking about. Should have made that more clear.