Yep, ppeatfruit a traditional fruit cake for a wedding cake takes an age to make, an age to cook, an age to cool down enough to ice properly
My favourite final challenge was the Afternoon Tea one, to me it was much better than the latest ones - just make a really out there cake - as it tested their skills on bread, pastry, cakes and presentation/decoration. I think they should do that in the final, just a well decorated cake is a bit of a let down imo.
Perhaps they could do something like a childrens birthday party, adult coffee morning, etc., and insist that it includes cake and pastry items and sweet and savoury. Also give them enough time realistically to complete it, I think the Afternoon Tea one was from early morning until about 4.00 pm, and if it is something like that they should allow some preparation time the night before.