Personally, I think the fairest way is to give us 1/12 of the required tier points (or 10% if CX wants to be nicer) for every month where many flights are cancelled and people are unable to travel. For example, 25~30 / 50~60 / 100~120 points for SL / GO / DM, respectively in Feb. and another installment in Mar. If some people get mid-tier benefit as a result, they can think of it as a nice gesture.