I’m not sure how this would work from a UI standpoint, but I do think something like this would address my concerns - even if it was coupled with a dire warning about how you probably shouldn’t be doing it. I absolutely agree with the principle of “doing things through the bank UI is better than using the journal”, but i’m a little nervous about not having the journal available as my “hammer of last resort” in case I hit a truly intractable use case.
One way that would fit within the existing UI would be to allow the accounts to be targeted, but only by going ‘through’ the associated control account - sort of like how Special accounts work now. You can even put up a 
sign in the UI to indicate that maybe this is a bad idea. But I still think it should be possible, even if difficult and/or discouraged. Just a thought.