This is the sort of thing we wanted arch for. Unfortunately, the way we use CVS means that we can't really do branching as only AJ commits. So, if it's not possible to do the migration without breaking things temporarily, there are three ways forward:
Well, why could we not live with DX8 / DX9 breakage for some time ? At the time D3D was resurected, it was broken for most of the time (and probably still is :-) ).
And if someone disappears from development, it's just more motivations for others to pick up the work and continue (which would be more problematic with branches as this branch, if unmaintained, could really wither away without anyone working on it).
Lionel