I know for personal experience that messing up with the formatting of a project can make history very difficult to read.
If reformatting is desirable then I would egoistically prefer to do it immediately, because this code base is new to me: should I need to understand something from history, I'll look at the history before my changes. But of course I don't want to make other committers angry :-)
If we agree to make a full reformat of the code base, I would first make sure that the formatting preferences comply with the coding style documented in the Wiki, and maybe enable also a number of additional save actions (for example, to add @Override where missing) and then run a full "Source -> Clean UP..." on all projects.
Also, I remember that some Eclipse projects use static code analysis also to verify that source code is properly formatted (I remember Gerrit refusing a patch of mine because the formatting did not comply with some formatting rules). Is there anything like that in place for Virgo?