The doctrine/task limits were capturing a reasonable average for the
era, but it did a bad job for cases like the Harrier vs the Hornet,
which perform similar missions but have drastically different max
ranges. It also forced us into limiting CAS missions (even those flown
by long range aircraft like the A-10) to 50nm since helicopters could
commonly be fragged to them.
This should allow us to design campaigns without needing airfields to be
a max of ~50-100nm apart.
An HTN (https://en.wikipedia.org/wiki/Hierarchical_task_network) is
similar to a decision tree, but it is able to reset to an earlier stage
if a subtask fails and tasks are able to account for the changes in
world state caused by earlier tasks.
Currently this just uses exactly the same strategy as before so we can
prove the system, but it should make it simpler to improve on task
planning.