Either you have to have prerequisites or you have to make that skill
only available at high levels via ioctls. But the ioctl approach has
many problems too. It is fairly reasonable if there are only very few
unconnected skills. But as soon as you start adding many partially
overlapping skills, you start having problems.
People will want to specialize which the ioctl approach doesn't
allow. And the flat independent approach has the unreasonable
consequence that someone who knows how to build small clippers would
need just as much time to learn how to build large clippers as
someone who has never been near the water.
The dependent structure for skills fixes both these problems. You
could have a USE-less skill called shipbuilding and in addition a
'build clipper' skill (for which level 1 requires shipbuilding 3) and
a 'build large clipper' skill (for which level 1 requires 'build
clipper' 2) aso. This would not necessarily have to be a tree e.g. it
sounds quite reasonable to have an assassination skill for which
levle 1 requires eg. stealth 8, but skill level 4 requires eg. combat
5 in addition. You can make this arbitarily complex to reflect all
kinds of interdependencies.
This would not have to be documented. People would find out about
their requirements as they advanced in levels. I think that this is
both in perfect agreement with the hidden complexity theory and your
latest requirement that players be given some idea why what they
tried worked/didn't work.
Anybody any comments on the idea to drastically cut down on the
effectiveness of STUDY without a teacher ? BTW, the teach command
already is in there and a provision for payment in teaching really
isn't necessary as you already can control who stacks with you.