Minimizing disk usage in a RAM-disk based system is performance-critical. Most embedded systems are low-memory systems, at least by desktop standards. A 2.2.14 kernel will boot and run in 4 MB, but there is little room for applications in this setup. Linux is quite sensitive to low-RAM setups. We might be exaggerating a little by stating that doubling RAM on low memory systems will increase overall performance just as much as doubling CPU speed.
A RAM-disk resides in buffer cache, so increasing disk usage will reduce available memory. This implies that we should review strategies for optimizing performance, and also makes clear why dynamic disk usage during boot-up is not really a critical point (as long as you never try to exceed available total ram, which can happen if you try to put the entire system into a single archive file). So, there is little necessity to reduce the image size of the booting system, as only run-time size is relevant.