> The architecture of lambda may prevent this.

It doesn't; you've always been able to use any language you want, by embedding it within the runtime of a supported language. This is just announcing proper, official support for it instead of having to rely on a workaround.

Lambda's execution model is language-specific runtimes being fed events off a queue through a single well-defined RPC or RPC-like entry point, with the process frozen or discarded upon queue exhaustion.

So the architecture of Lambda may indeed be a severe mismatch for running arbitrary containers.