the /v1 API does not allow users to specify which fields are returned. the /v2 does allow users to specify which fields should be returned, but it is in active development, and its use is not recommended at this time. so then that means the best approach right now is to parse the /v1 results as you need them. (i’m guessing that parsing is what you mean by “brute force strip out”, though the way you describe this suggests that you might be planning to do the parsing in an inefficient way.)
note that this would have to be computed on your end and is not provided in the API results directly.
you work with what you have. if you already have a script to get data in the way that you want, it’s relatively easy to get the data. the time-consuming part is writing the base script you need to get data.
i don’t have anything already written to get exactly what you’re describing here, but you could adapt something that i wrote to get /v1/observations to get /v1/identifications instead. see: https://forum.inaturalist.org/t/whats-the-best-way-to-share-python-code-nowadays/48554.
pyiNaturalist might be another thing that could help you get data more easily.