Founder -> Product Manager is probably the only way I've seen which produces good PMs for startups. Startup PM is totally different from PM in a big organization with great process and resources.
The company I now work for (CloudFlare) seems to have 100% of the PMs come from startups (including me), either from acquisitions or direct hire. It works really well.
We're also looking for a head of marketing. Email me (rdl@cloudflare.com) if you're interested, although I'd also strongly recommend balajis.