Hi, I really wonder why are yo sticking to PHP? In the end you will just have produceed another island software that is very uneasy to integrate with $ANYTHING. Instead if you develop a django app this can be combined with very little effort with all things django and opens up the world of incredible python modules.
Seriously, please take one month to implement a flarum protoype in django and you will understand what I mean.
Also python is in fact more easy to deploy, because you do not have x thousand settings in php.ini and serious problems with different versions on different hosts. Also python is definitely easier to use for tech-savvy but non-programmers.
Please do not stick emotionally with your tools. As experienced PHP devs you will pick up. Python quickly. It is such a much better alternative, please do not make this mistake to build another forum with php. Thanks!