That's a very similar use case to where DTL started.

We needed a way to link arbitrary APIs together without having to resort to custom code to rewrite the data between formats. DTL was born as a way to handle that translation without having to worry about untrusted code or limiting the end-user's ability to define how to remap the data. DTL can only operate on the data it is provided and can not rewrite the input data as it runs, so it is pretty safe to use in that way.

I'd love to see DTL get used in the way it was originally built for. Happy to help / talk sometime if you want.