Hi Thomas. Olaf said some of the things I was thinking. In short, I think this plan is too clever by half.
Repository conversion is repository conversion. It's not an opportunity to rejigger the history. It's a fundamental failure of what the repository is there for if it loses or divides the history. There is no problem with the size of the history. Once we finish converting to a new system, then we can worry about any kind of reorganization you might want. Thanks, Roland