First, I'd like to +1 this, as I'm currently in the early stages of planning a new project where domain.com would host the main website (including a shop and backend) while api.domain.com will provide several services that don't have to be tied into the main site but probably will use the same database.
So I will probably have two projects (one with Lumen and one with Laravel). My question would be what would be the best approach to tie both projects together. For example I would want both projects to have the same Eloquent Model classes. Is there a best-practices article on how to outsource a Laravel API to a seperate Lumen project?
Regarding your question: I think what you are trying to achieve won't play out well with Lumens approach. Actually, Taylor talked about this in the latest Laravel Podcast. Maybe take that one for a spin?