I agree - I think 7000 for conspicuity was a very silly idea.
Our aircrafts' TXPDRs (Collins) are the same as Corporate Yank's - they switch themselves to standby when you twiddle until five seconds after the last input.
I appreciate the controllers' points of view regarding problems over briefly selecting a code that might trigger a flight plan, but for TCAS point of view, however long it takes (within reason) I would prefer to have my TXPDR interrogating another's.
Okay, the first might well be thoroughly inconvenient. The second might be thoroughly dangerous! And let's face it, whilst we're trying to avoid errors, we're also trying FIRST AND FOREMOST to eliminate danger.
So let's have those transponders on (please?)
As a sideline, I would also prefer use of a transponder Mode C mandatory. So often controllers pass us "Slow-moving traffic your twelve o'clock, no height information". If we're under a RAS and can't see it, he HAS to give us avoiding action, even though the chances are it's more than 10,000 below.
So instructors, please teach your studes to use Mode C at all times.