I dont think that is possible, the .dbc files are generated by the launcher so if it cannot install the sims3pack you are stuck ... you can use your previous items using that trick but that is it.
Either EA fixes this mess or Sims3packs are a dead format.
Actually the sims3pak works fine from every site but the official Sims3 site. If you want something from the store the patch now apparently monitors what you have paid for and what you have not. I had 2000 points from promotions. Everything that I obtained legally works fine. All of the sims store content that I have obtained from other sites are useless. I have sims3paks from SimsDesign Avenue and Around the Sims 3. Those are working fine.