I turns out R does not natively handle 64bit integers. There is some warkarounds that have some drawbacks (casting as string -> slow performances ; casting as numeric -> can introduce silent errors (just try 2^53 == 2^53+1 ) ; using packages -> some other packages are not compatible).
In a federation/big data perspective, this might become a problem in several years, or is already a problem.
However handling 64bit natively looks not that trivial for R-core
At this step of the project, it might be important to discuss this limitation for a stable future. I do not want to troll but python does not have this limitation, and is growing fast as a statistical/machine learning web language .
I guess that is better than nothing to discuss of that, and maybe mixing OMOP to python could be of interest to enlarge the developer community, at least. An other approach would be to help the R community to get rid of this issue.