If this makes you switch to Trump, you were always going to.
No.
If Biden came out for court packing that would make me
have to vote for Trump, and I think I've made it quite clear that is something I do not wish to do. In fact I tend to vote straight dem now just because my current test is if a candidate would have impeached him.
Judges are the only thing that makes voting for Biden a huge moral challenge - but its ameliorated by the fact that he would only get one or two in the normal course of things. Weighted against the abject evil of Trump's treatment of refugees, silence on the genocide in China, locking of children in cages, makes Biden support acceptable.
Court packing changes that calculus. A packed court will certainly cause more long term evil than another four years of Trump. He would do great harm - but the unimaginable destruction of a liberal court would inflict upon religious liberty and the right to life would become permanent.