In Symfony 2.7, we made it possible to use most features of Symfony without enabling the templating component (assuming you don't use a bundle relying on them of course).
However, we have 3 shortcut methods in the base controller which are not compatible with such setup and force the usage of the templating component:

• render
• renderView
• stream

Most projects based on Symfony are probably relying on them, as this is the documented way to render templates.

All of them can be implemented on top of Twig directly quite easily. I suggest doing this in 2.8 in case the templating component is not available.