It would be nice to have the infrastructure for this in LedgerSMB. We should definitely have a feature request open and an eye to do it.Even for #2 there is a lot to be said for having a single place to check whether warranty is handled.
I probably won't personally be able to direct much effort towards this until after the financial rewrite but would be happy to help those anyone who wants to do the effort. (I would probably take it on as a paid project before but to be honest this is one of those things that would probably cheaper to do after.)
At this moment I can manage the warranty issues in a ticketing system, inside my egroupware system, as I cannot handle this kind of situation with LS.
So, I think it is possible to do the same thing in other open source tool, like in an issue tracker.
The 1st point would be nice to include in lsmb. I guess, extending the parts table could be fine, but of course, to register the actual value for invoices, offers, orders would be necessary, too.
Cheers,
István