Sorry, but I can't support this as a solution.
Many vehicle drivers put their indicators on when they start to manoeuvre, not as advance warning that they are going to. If I get crushed against the pedestrian railing by a lorry that turns left alongside of me, it will be of small consolation that the last thing I see is a blinking amber light.
As others have said, don't overtake a lorry - on either side - if there's any chance it'll turn across your path before you get past it. This isn't about cowardice or lack of assertion, this is the same kind of prudence as "don't overtake on a blind bend" or "don't overtake on the approach to a zebra crossing". Sure, these vehicles are big and have crap visibility, but people don't choose to drive them because they're aggressive or full of themselves, but because they need to get large amounts of useful Stuff from A to B. I'll cut them the same slack they need to do that as I expect them to cut me when my road positioning is stopping them overtaking at a pinch point.
"I never overtake a lorry"
I do, often. But as with any overtaking manoeuvre, I do it with a significant speed differential (a common situation is when it is stopped at lights and I know the red phase has a while left to run) so that I can get past it safely and resume my place in the normal traffic flow.