Wouldn’t universal salvation remove someone’s free will choice?

Perhaps, but no more than freewill being removed when they were born without choosing to be born.

If eternal torture in literal flames in a body that cannot die is someone’s destiny, it would be ridiculous to claim that they consciously chose that over bliss in heaven. If they do then they are mentally ill and are not qualified to make such a decision.

Our own earthly legal system wouldn’t even allow for such a self-harming decision to be made, assuming a competent attorney were able to make some basic arguments to a judge. The judge would say, “There’s something clearly wrong with this individual. The court will step in and make this decision on his behalf.”