I agree. Handling support for this type of product is definitely a challenge. Especially since many customers don't have any experience installing anything on their servers. I've tried to make the installation process as simple as possible (It only requires database credentials), but many customers still have issues.
A free-to-download "test my environment" script could be a good idea to mitigate some of the installation issues. Write a simple one-file PHP script that a prospective buyer can download for free, and run on their target environment. That script can give them a report showing them what works and what doesn't.
This could save you a lot of post-purchase support requests.
