There might be, but it's probably less common than DIY installs. It'd be great if someone offered that. I'm guessing a 6kW system only requires ~40-60 man-hours of work, which is only ~$1200-$1800 at $30/hour. But most installers would rather keep the ~$15000 for "installation" than farm out the labor. It'd be a pain coordinating everything, but for $15k, probably worth it.
Having said, that, I'm guessing that by the time you familiarize yourself to the point where you can manage your contractors, you can probably DIY if you don't mind the labor.
I'm guessing that's why there's so much interest in DIY installs. I've been pricing/planning out a system, and even using high efficiency (18%) panels, good mounts for concrete S-tiles, 4/0 cables to minimize resistive losses, etc.... I doubt I'll break $2/W.
Have you asked on solarpaneltalk? Someone might have had experience farming out some or all of the work.
https://www.solarpaneltalk.com/