This may seem a little out there, but I was just kind of wondering if it could be at all possible to convert XML files containing the linkset codes to an LLSD (Linden Labs Structured Data) object. I know it would involve hacks and a lot of complicated programs to be able to do it, but I'm just wondering if it's POSSIBLE.
I'm thinking the XML document would be imported by some program onto MilkShape 3D and then saved to a file to be imported to the game...
I'm able to create really nice objects on Second Life and texture them way better than I can with Sims 3 objects. I'm terrible at MilkShape t-e-r-r-i-b-l-e, but I've always wanted to create my own meshes for the game.

Sorry if it seems farfetched, I'm just curious and I would like to discuss it with my fellow Second Lifers and Sims 3ers! :D

Almost anything is possible - but you wouldn't be allowed to convert TS3 content to SL (EA owns the data - they allow it for modding TS3 but not anything else) and there are no plugins that I know of to do it - and I think it'd be a pretty safe bet that none exist. You could try writing plugins yourself, but it sounds like that would probably be over your head. So... possible, perhaps. Doable... no, not really.