The best way to hide your tracks is to legitimize the activities you participated in, supported, and help fund in order to obfuscate the money you have made while doing so. This was the strategy that Hillary Clinton used with Uranium One. She used her dealings and activities in an official and quasi-official manner with Westinghouse to obfuscate her Uranium One sale and profit.
In the meantime a simple request for criminal proceeding transfer on one of these cases involving US officials and or citizens committing crimes in the Ukraine is the fastest way to bring justice on our own time with results so cases don't magically "close" like they do in the Ukraine.
All Inspector Generals are working together there is a lot of inter-intra agency talk and sources say NSA is a bit out of the loop. It’s important to remember that Horowitz report is simply an audit/fact finding.