1. I see in the sub-forum you guys are changing the terrain up a little. Currently, Rugged terrain does not terraform. This makes it extremely poor terrain, particularly in light of my concerns with other aspects of the terraforming civic (see below). Perhaps Rugged should only terraform into plains?
2. Currently, building a Reservoir of Liet yields thats -2 diplomatic penalty with, I believe, only civs running the pro-spice civic. A few problems with this. First, if you convince them to switch civics to Arrakis Paradise (side note: I wonder if you should even be able to do this...), you retain this penalty. Second, if you disable the terraforming victory condition, you can accumulate enormous negative diplomatic penalties. Its enough to overwhelm every other factor in diplomacy and basically means you will never trade with a pro-spice faction for the rest of the game. Perhaps cap the penalty at -8ish, or perhaps -10 max total for the Reservoirs and the current -4 for using terraforming. It would be nice for two civs who are strongly the same religion but clearly differing on the future of Arrakis could still trade techs and resources.
3. At least in my games so far, the vast majority of civs switch to pro-spice. I think this is because they research it first as it is a much cheaper tech and comes sooner in the tree. It seems like a civ immediately switches to the first Arrakis Future civic they get, unless they are, what I assume to be, hardcoded to prefer one over the other, i.e. Corrino for pro-spice and the fremen for paradise.
4. At regular speed, at least the first half of the entire tech tree goes by way too fast, even with no tech brokering. Increasing tech costs by 25-50% wouldn't be crazy, in my opinion. However, it is actually fairly well balanced on epic speed, so maybe its just a personal preference.
5. I still think the pro-spice civic is way too weak, especially versus the terraformers. Spice in general is still way to weak as well. I don't feel like it is a must-have thing right now, which makes no sense in the Dune universe. You get a modest economic bonus for each one right now. Why not, at the least, a much larger CREDIT bonus in the capital for each resource? Since upgrading in this mod is SO expensive, this would provide a great incentive to devote more energy to mining spice.
6. Related to 6, I think upgrade costs should be decreased; significantly so if you don't implement 5 above. Planetfall has done this well, I think.
7. I know this is probably pretty far down on your list, and I've already complained about this before (sorry!) but city placement remains god-awful. I know this is more of a base civ 4 problem, but its effects are much more pronounced in this mod because water is relatively scarce. While I know I can change the following myself, maybe force the AI to settle a minimum of 3 squares away (it is 2 right now, right?). In fact, this may be blasphemy, but 4 squares might even be better. Much less cities, but much better quality ones.
8. Really minor quibble, but the tech that lets you build a library immediately precedes the tech that lets you build the observatory. Seems just a bit odd to have two research buildings directly next to each other. And, by the way, the name "observatory" doesn't really seem to fit the Dune theme. Hate to criticize without offering an alternative, but I can't think of one right now.
9. It would be absolutely amazing if terraforming lead to the development of oceans and lakes as mentioned above. The contrast between the terraformed lands and the rest of Dune would be great to see. No complaint here, just a hope that its possible to do.