Like I said, anything's possible
Assuming the game itself can't help, you'd need a plugin/program to monitor the current car damage/state, probably periodically send that data to the server in case of dropout and send at key moments (end of session, leaving server, etc), then when entering the server (or perhaps at the start of a new session) query the server to ask what the current state is, get that info, and re-apply it to the client.
That leaves you needing to find the various damage states/values, the connection status so you know when the server has been connected to, a server-side program to receive the ongoing damage data from clients and send when requested, and the game letting you apply damage/other state to the car without being rejected as a potential cheat because a lot of those same values could be cheat targets.
It seems plausible, but that last bit could cause issues.
To answer the question in your first post more directly, 'damage' isn't accessible at all by plugins. You've got stuff like dent severity around the car, last impact position, time, magnitude, but nothing to do with engine/brake wear, suspension damage, or that kind of thing. Basic tyre condition is available but not in any manner that would be worth trying to apply to the game. So everything would need to be found in memory, and applied in memory. Very similar (if not identical) to an exploit.
*Just so I don't give the wrong impression, I personally wouldn't pursue this. For me it's a lot of hassle to end up with something that ISI would probably frown on anyway, would probably need very frequent maintenance for similar reasons, and eventually (hopefully) would be surpassed by improvements ISI makes. But it's a free world
