It is going to be interesting seeing how they balance it (and actually in the main Doctor Who show as well) when there's literally an entire second Doctor just sitting there doing nothing. Like anytime they escalate things to world-threatening stakes, it's going to feel weird that there's a version of the Doctor there who could absolutely help but just... doesn't for some reason. Like I know this Doctor's supposed to be recovering and taking it easy, but it seems a bit out of character for any version of the Doctor to not help when people are in trouble.