Does the current or new JMS inplementations allow the sort of multiplexing that if a large message is sent from a->b followed by a really small message from a->b, that the small message could finish going through the wire before the large message?
The RMI Connection Factory will let you do that.
Somebody tried to write one in the past.
It was buggy when I tried it, but one reason was a bug in NIO
under windows in java 1.4.1
I think it is included in the 4.0 distributions? Maybe
you can fix it or use it as a basis for one that works?