The problem is “what is generic?” You use PHP as a server side language. Some people use other languages. As a developer of such an add-on it would mean all kinds of people asking to add support for whatever language or Apache module or anything like that to add to the HA add-on. I don’t think this would be a good way to spend HA development time. If you install HA on your RPI on top of a normal raspbian image using docker (explained on the installation page in the documentation on the HA website) you can choose from the many LAMP docker containers on docker hub to run on the side.