I would also note that, on top of making the new unit at Chemistry, it has the effect that you keep the Formation--Field Works split into the Renaissance. So you drop Field Works from Tercio (and adjust UUs accordingly) such that there is still the "strong Iron-using" Unit and the "weak, resource-free" unit. This is, again, in principle independent of moving Pikeman earlier, but having Pikeman at Steel makes more sense if they don't upgrade into the same unit as the Longswordsman. So, on point (2), if you introduce Greatswordsman and do the Formation--Field Works split, there is less reason to move Pikeman earlier. However, even then, on balance I think it would still be desirable, just because Knight-versus-Spearman is so awful.