Premise 0: You are BFR-PR for the tax year and hold an Act 22/60 individual investor grant effective for the tax year
Premise 1: We are not considering whether or not to make trades. We are taking the trades made as a given, and only considering what form of specific accounting to use in calculating gains (e.g. FIFO, etc).
Consequence of premise 0: You get no benefit from any losses realized and you owe no tax on any gains realized.
Therefore: The basis of your current holdings should be maximized so that when you no longer have either Act 22/60 or BFR-PR status (or both) in the future, those future gains (losses) will be minimized (maximized), resulting in the lowest taxation.