[Elecraft] K3 Diversity antenna settings - wish

[Stewart]

I want to set my K3/100 up for diversity reception using my main 
antenna (doublet) and a receive loop with with pre-amp.
The K3 is fitted with a  KAT3, KXV3 and KRX3.

As I wish to keep maximum flexibility of antenna switching I do 
not want to use the AUX BNC  for the Sub RX as it stops me from 
easily using either the main antenna or  loop as Sub RX input. I 
don't want to be reconfiguring the K3 hardware as my needs change.

The setup I have arrived at is 

Main RX - Ant 1 - Doublet
Sub RX - Ant 2 - Loop pre-amp (with output switchable to RX ant 
input)

This works, but obviously has the potential to damage the loop  
pre-amp if I accidentally transmit to Ant 2 connector.

It would be nice if a Ant 2 TX inhibit per band were available.
Is this possible ? 
Maybe there is a more elegant solution that I have missed. 

73
Stewart G3RXQ