John Stevenson is the go-to guy for experience with shaft build up and restoration.
I also seem to remember thin sleeves available for needle bearing inner races that might have some application.
Are you positive there isn't a way to persuade your lathe to produce a metric thread? I do metric with some regularity on an old Atlas. And (since you have an affinity for special tooling) there's that slide mechanism to produce ANY thread you want. It's essentially a secondary longitudinal slide under the compound linked by a bell crank to a track fixed to the bed. This track can be angled so the thread actually cut will lag or lead the thread set by the leadscrew. I'm not sure I've saved any pictures but can probably track something down if it's not clear and you're curious.
"In theory there’s no difference between theory and practice. In practice there’s a lot of difference.” Yogi Berra