How about shipping cache/compiled with permissions set to 775 instead of 755?
The file owners are set to the developers responsible for them. The webprocess/php gets it permissions by being a member of the group owning the files. This arrangement is published as a best practice at serverfault.com, for the case where webfiles are maintained by a group of developers.. link: http://serverfault.com/questions/357108/what-permissions-should-my-website-files-folders-have-on-a-linux-webserver
Running exec is dangerous only if parameters entered by site visitors are used, which does not apply to this case. Regarding the speed of exec, it is fast running nothing but whoami, unless the server has a problem that would be affecting all the sofware it runs, not just Grav.
Unless you do something to Grav to prevent this 500 error, I don't see how you can have credibility when the download page says "Simply download the ZIP file, extract it in your web-root, and you are ready to start using Grav!"
Two developers from our shop downloaded and extracted into a webroot on different se rvers and both of us had problems. There is nothing wrong with either of our host environments and neither of us made mistakes. The problem is that Grav has some holes in its portability
What is it with CMS makers that every problem with installation is a problem where the host has something wrong? It is not just Grav, all CMS providers do this. Since the CMS providers typically have developers speaking to customers who are non-developers, the customers are intimidated and basically humiliated into accepting that there is something deficient in our systems and our brains that is the cause of our installation problems. Why don't you take responsibility of a disappointing customer experience, tell your customers that you are sorry for the inability of your system to adapt to their environment, and then make it so it does adapt? Even if the end result a product to what you deliver now, that service attitude would make your customers think you are great instead making them feel like they are incompetent. Your customers we not incompetent. Your software falls short of meeting our needs.