Some experiments show that by moving all of the non-class files out of rt.jar, we could get some speed up on the cold startup. Here are some cols startup data based on b50 using MetalWorks demo in JDK. That demo loads a bunch of gif files from rt.jar during the startup.

(Unit: ms)
Trial # B50 B50 (move all the non-class files)
1 4984 4109
2 4766 4188
3 4313 4140
4 4860 4141
----------------------------
Average: 4730 4145

So from the above data, we could get pretty much 12% speed up on the cold startup for these applications which use resources files from rt.jar.