I sympathise with you on the polylingual tendencies. I'm currently working on something for one client that uses several different programming languages plus the usual web-related stuff all on the same project (and with perfectly legitimate reasons, not just because of historical baggage).

Still, I think this raises an interesting question: is it more beneficial to choose exactly the right language for each project in isolation, or to adopt a "good enough" general purpose language that can be learned in more depth by the development team, and used together with comprehensive library support and a strong and familiar IDE?