if it is in replace mode then there should be a way to provide the current functionality. as some times artists also want to add selections based on multiple layer elements. for example suppose you have a character whose body parts are spread across various layer you just go on selecting the layers and doing select opaque so in the end you'll get entire character in selection. after which the user can go on to add a mask or do some operation over it.

in my opinion if we are going to modify this behavior there needs to be a way to accommodate the older behavior too as there may be artists who have created a workflow based on it. Ctrl +click on layer thumbnail to load selection is cool too.

Ok, sometimes needs just selecting opaque from only one layer.
Sometimes needs add opaque from another layer in to current selection.
Sometime needs subtraction opaque (but we may do it with first two and inversion).

For normal selection we have hot-key Shift+'Select'. It's adding new selection to current selection.

So, maybe:

1. Shift+ ClickOnLayerPicture (in LayersDocker) — it's good for adding layers opaque to current selection.
2. Ctrl+ ClickOnLayerPicture (in LayersDocker) — it's selecting layers opaque like replace. That's works in Photoshop (AFAIR).