i think avernum needs more possibilities.
in a2 and 3, there is only one large storyline you have to follow. in a1, there isnt any at all, really.
i would find it much more interesting if it was more like the EV series.
a huge world, filled with different plots, races, etc etc etc and you can choose where to go and which line to follow.
for that, it would be good (though not necessary) to be able to choose more kinds of PCs.
(just imagine playing a cave slime destroying the human race! )