schema.org/WebPageElement and it's subTypes

Now that mainEntity/mainEntityOfPage are out of the way I'd like to bring
up schema.org/WebPageElement, it's subTypes and the 'mainContentOfPage'
property.

For a long time I've been wondering whether or not there's any sense in
marking these elements up as they describe the HTML elements on a page,
rather than the underlying real world entity that is described by other
markup. On top of that their schema.org pages provide no examples on how to
use them nor do they seem to have been worked out such that they are easy
to specify.

For example, if I markup an event widget as a schema.org/WebPageElement,
how would I indicate the widget contains an schema.org/Event - should I use
'about', 'mentions' or 'mainEntity'? And what if a WebPageElement contains
multiple entities, should I then use 'about' or 'mentions' or do we need a
new property for this?

And what about the relation between WebPage and WebPageElement? 'about',
'mentions', 'hasPart', 'contains' have all been proposed in the past but
neither of 'm got any large scale support by the participants of the
mailing list. Meaning that until thus far there doesn't seem to exist any
valid method for chaining WebPageElement to WebPage or chaining
WebPageElement to the entity/entities it contains.

Dan Brickley once even expressed he was wondering whether these Types
aren't a form of markup for markup's sake as opposed to providing any
serious value. A point of view which I've step by step have grown to agree
with and therefor I wonder, might it be an idea to deprecate WebPageElement
(and its subTypes)?