Well, it's pretty clear by the degree of support that I'm the only one who thinks this would be a good feature to incorporate into the IDE, so it's probably best to just forget that I posted this suggestion.
I did it again this morning, and tried to 'upload using programmer' to an ATtiny85, wondered why it wouldn't upload, then realised that when I selected ATtiny, the board setting had defaulted back to the ATtiny45 because I'd uploaded to a UNO just beforehand.
I'll learn to live with it. 