Thats pretty much my plan, add an offset that periodically changes. This will keep everything positioned within the 32 bit FPU sweet spot and since all object positions will be relative to the cached terrain tiles this will have the side effect of making my databases more storage efficient as well and also allow me to wrap coordinates for round or toriodal worlds without the complication of having objects crossing signed boundaries at the wraparound point.
YIP! YIP!