WHy not have the modulation transformer output be another position similar to RF envelope,... that is a simple O'Scope mode. You might consider adding a tone generator as well, perhaps a single tone and/or two tone.
Good point. I'd like to encapsulate any test modes one would use on a transmitter and have it all self contained in one package and then perform any test at the flick of a switch. The more the merrier. Thanks for the idea.