[BenMorganIO]

I would start with asking the backend and front-end developers to learn Laravel and begin using it. All code review should be quite strict. It's going to suck for a while, but that's just the way of it.

Set up two nginx servers. One that's your usual to load Laravel and the other to the legacy nginx server that acts as routing to the legacy application. I would even recommend using OpenResty to help delegate if you need something intelligent.

I would strongly discourage a JS framework that would add increased complexity when you need to keep things focused. The front-end would need to be recorded in Laravel and brought back over in a clean fashion.

Set up a CI and ensure all the code that goes over to Laravel is near 100% tested. Might also be useful to set up a visual regression test tool such as Percy to ensure everything moves over nice. Push for SMACCS and BEM to keep things consistent. Or just make new styling for the new pages to surprise the users.

Rewrites are a trap though and can be painful. Keep a balance of features entering Laravel and the big foxes entering the legacy app. I would recommend RabbitMQ to communicate between them.