I have a large existing web application that isn't built on Symfony. It badly needs some improvements that are too difficult to make because of the structure of the code.
Rather than start from scratch to build a 100% brand new version of the site under Symfony (which will take months and nothing happens on the existing live app in the meantime), I'd like to try a hybrid approach. I would carve off a \~standalone piece of my app and rebuild it in Symfony, then swap out that chunk on the live app so the Symfony version would be running alongside the rest of the (legacy) app. Lather, rinse, repeat until the whole thing is under Symfony.
The goal is to keep up development on the main app and make structural improvements along the way while transitioning the whole thing to Symfony. (And yes, I realize that in practice it won't be this smooth and sometimes the pieces of my app will dramatically overlap, causing much heartache and hassle... but for now let's pretend my app is relatively modular and can be easily broken down into standalone chunks.)
I assume this is *possible;* my question is, would it be a good idea to get my app updated into a nice modern sexy framework?