1: It's true that Rubber doesn't get used for much, but adding toooo too much complexity to early recipes is not great, and I already added a whole bunch of complexity with my revamp. I tend to find it better to keep the number of different materials low early on, but increase the number of steps to make the production line more interesting. But Rubber does find more uses if you add AAI vehicles, since at least a couple of the early ones need Rubber for their tires. The later ones all use Vulcanized Rubber, of course.
2: I don't really see much that can be done with Tin, even if new types of processes are added. The way it's purified is just simple carbothermic reduction, and the carbon part of that tends to get ignored in Bob's mods.
3: It's better not to have too many machine types. I originally considered having multiple machines for what is now just the Machine Shops, but however I split them up, it always felt like there weren't enough recipes to go around. Having too few recipes on certain machines like Distilleries and Centrifuges is something I've always been trying to correct, with... some success.
4: I don't really see any need to have more oil processes than already exist. There's one that only produces Sour Gas, another that produces Sour Gas a lot more efficiently, one that produces a lot of Light Oil, and one that produces a lot of Heavy Oil. That should be basically all that is needed. Creating new ones that produce Light Oil or Heavy Oil exclusively would be possible, but it would be bad to make working with oil too easy.
