If you want to bring sales skills into the mix then you need to know your target market segment. Selling cars to the public is not the same as selling robots to the corporate world.
Startups also should have multi-tasking founders. Ideally, all of you can do several things. It can be a mistake to think that person A is a sales person, person B is technical, person C is design etc. because you then need 6 or more people just to cover all the jobs.
Also, you will possibly come up against problems with investment if a Founder is seen as dead-weight rather than adding value.
Just my tuppence worth!