good idea for a mod? what do you mean, someone edit the gamefiles themselves and make a patch or something? i mean for climbing ofcourse.
though as what i see in the latest of computer technology, morrowind will be reduced to requiring only a quarter of the ordinary home computer stat specs in only a matter of months now. as the latest cpu's from athlon produce about 20 % better than others from intel etc..? (not entirely sure about that last one, tho..

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but is it possible to actually edit the game, and make the climbing possible? i spoke with a friend today, and we discussed how it could be possible to make it happen, and we reached the conclusion that if only surfaces were climb-able, it would be a matter of skill to be able to hold on to these different surfaces, and that maybe there would be different surfaces requiring better skill levels and so on and so forth. btw, there should also be a matter of different surfaces, depending on race or class, like kahijts would be able to climb trees more adequatly that humans etc.
and, yes, I did mention the possibilities for it appearing in a sequel..;P