Hi Michael,
This looks great. It is something I have been planning to get around to doing for some time but hadn't got around to it. If you are interested, it would be great if you would consider making this part of rOpenHealth. We are at a much earlier stage than Scott, Karthik and ropensci but we are growing and I think a collaborative project for r interfaces to healthcare and public health APIs and data will be a real asset to the community.
clinicaltrials.gov is the most obviously outstanding of these at the moment.
If you want to chat further, you can email. I'm happy to give you full admin rights to a repo in the group, any further support you need to e.g. get it on CRAN (looking at the code I doubt if this will require much work), plus hopefully a little publicity. One of the problems I noticed, like you, when I looked at doing this was the complexity of the different tables to be downloaded.
Best,
David