Hi Robbie,
Actually my thought process was not to give a "bonus" per say, but try to incorporate somekind of strategic value to terrain. As it strands it offers minimal impact on combat, and will prevent you from building on cliffs, mountains or forests. There is no difference if you build something on a swamp or Arctic. I think that something should reflect this aspect.
I wouldn't mind if it were in terms of build time or extra material costs, I just want "something".
Although, I would be interested in seeing more terrain specific buildings. Farms on Plains & mines on mountains? To be fair, I wasn't part of the beta and from reading certain posts I noticed that some people were saying that "back in the day" it was possible to build farms, and then people just had that. I think the key is balance, so make sure that the costs for making a farm are high enough so it's not easy to just spam those buildings. (high GP upkeep? Material used / turn, only 1 per city, something.)
I would of liked to see more terrain exploitation, and make the 'resource nodes' just extra bonuses, a bit like how civilization or Master of Magic would do it. This would make it so that even in the absence of 'ressource nodes' terrain still needs to be considered when building a city. Which is not so much the case presently.
Hope this helps flesh out my suggestion.
thanks for your feedback!
V.