I've said it before and I'll say it again, they need to do the serial system again, rather than make it a mini-series every year. Have the Doctor just go on mild adventures where the stakes aren't so serious or world-bending, lower the budget and save the big overarching story until the final season, then run it like you would now. That way you have proper foreshadowing of the Doctor's end of tenure. Then you can go back to lighthearted silly bullocks for a while.
Case and point:
War Games into Spearhead in Space, Keeper of Trakken/Logopolis into Castrovalva, etc. Etc.