Hi Andrew - It's been a while since I have used this, but have you tried using the "Post Data to Server" processing step? Basically, this processing step allows you to repost to another location. Unsure if it will meet your specific requirements, but would definitely be worth looking into if you haven't already. Otherwise, it seems like what you mentioned would work...using the initial Eloqua form submit to add someone to a program that then runs the Form Submit connector to push the data to your external form.
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