It sounds to me that you want pikes to fit the role you want them too, and not the role that the developers want them too. Just because you say that pikes are a front line infantry unit does not make it so. Clearly longswords are supposed to be your infantry for that time. Don't have iron? Well that is the point of strategic resources. You will suffer for a bit, having to use other units ( such as pikes) to deal. However that does not mean that is the main purpose of pikes, and as such they shouldn't upgrade into something they are not. If you are screwed out of iron the logical thing is to make due until you can get access to musketman, which is the point of the line. They are resourceless front line infantry units.