I know, Steph. LOL!
Darque, I think a good way to implement the whole ability to walk through mountains would be to have it as an automatically attached promotion. Like, in FFH, if you build the wonder 'Pact of the Nilhorn', the three giants you get (called Larry, Moe, and Curly [so damn original, ain't it]) automatically have hidden nationality. (Of course, as with all hidden nationality units in FFH, the giants can use the spell, if that's what ya call, 'reveal nationality'.) Similarly, the Dwarven units in general could have an race promotion, obviously Dwarven, that allows like +30% hills defense and the ability to walk through mountains (called mountain climbing). In the pedia for all Dwarves, you could put in something at the bottom that would say, "Like all Dwarves, the (insert Dwarven civ here) have mountain climbing, which allows them to walk onto mountain tiles".
Just something you pass to Greywarden, since I gather he's working on the pedia, among other things. I'd do it myself, but I don't know how to do XML. I'll probably learn it soon, and if you guys want, I'll help you with this in that way, as well. Although, (3rd time saying this), I lack the time because of classes. I go to South Dakota School of Mines, an engineering school, which has very hard math and science classes. I'm studying Mining Engineering, which means I have to take Chem 1&2 Physics 1&2 (among other things), in case ya wanted to know. So, that's why the Dragonia map isn't BTS yet and why I haven't learned XML yet either.