Yes — HotSpot does much of this, but the inability until recently to encode "call this function which expects some number of arguments" in the instruction set h

Yes — HotSpot does much of this, but the inability until recently to encode "call this function which expects some number of arguments" in the instruction set has historically been the limiting factor. invokedynamic helps a lot, but it adds enough levels of indirection that AIUI often enough isn't inlined for it to really solve everything. I wonder if a tracing JVM would handle it better? Probably.