Having just got a warm cape and a farsight telescope from Frostmarch (yay!), I’d like to suggest the following.
Why not give us the opportunity to play through the quest twice and therefore get two lots of those elusive ascension mats!
But… of course there needs to be a penalty to make it a fair exchange.
So I propose that on the second play through, a +50% WP levy is added to every level. This would mean that on the second play through of Frostmarch, you would need to sacrifice 30 WP to get the extra farsight telescope (and of course, pay the extra 50% on every stage before that). Yes, I know that means you have to be a certain level to get the 2nd crack at the final stage, but I see that as an added incentive to stick with the game and level up.