Never pre-positive adjectives and intransitive prepositions

The accepted response to an earlier question concerning words like alone, asleep and alive places such words in the category of adjectives that simply don't occur in front of the nouns or noun phrases that they modify -- a category labeled as never-attributive adjectives. 

There are other words that easily modify noun phrases which precede them, such as here and there.  These words fall under the category of intransitive prepositions. 

There are strong similarities between how the two categories presented are placed and used.  They both work well in post-positive, predicative and supplemental positions.  They both seem able to modify verbs as well as nouns.  In some cases (alive and asleep, for example), the so-called never-attributive adjectives derive from fused prepositional phrases. 

Is there a useful distinction here?  Is there something about never-attributive adjectives that isn't true of intransitive prepositions?

Edit: Since examples were requested . . . .  

Something that's called a restricted adjective:

Alone, that man can get the job done. -- supplemental placement
That man alone can get the job done. -- post-positive to a noun phrase
That man can get the job done alone. -- post-positive to a finite verb and its two arguments
Let him work alone. -- post-positive to a non-finite verb
You should keep him alone. -- predicative argument

Note that supplemental and post-positive to the verb positions carry similar semantics, quite distinct from those of the placement post-positive to the noun.

Something that's called an intransitive preposition:

Here, this man can get the job done. -- supplemental placement
This man here can get the job done. -- post-positive to a noun phrase
This man can get the job done here. -- post-positive to a finite verb and its two arguments
Let him work here. -- post-positive to a non-finite verb
You should keep him here. -- predicative argument

Ditto.

And, just for giggles, how about an obvious adjective?

? Happy, this man can get the job done. -- supplemental placement
? This man happy can get the job done. -- post-positive to a noun phrase
? This man can get the job done happy. -- post-positive to a finite verb and its two arguments
  Let him work happy. -- post-positive to a non-finite verb
  You should keep him happy. -- predicative argument

Note that, if "let him work happy" and "let him work happily" carry the same semantics, it seems possible that "happy" isn't an adjective there.

Further giggles, a transitive prepositional phrase:

In the dark, this man can get the job done. -- supplemental placement
This man in the dark can get the job done. -- post-positive to a noun phrase
This man can get the job done in the dark. -- post-positive to a finite verb and its two arguments
Let him work in the dark. -- post-positive to a non-finite verb
You should keep him in the dark. -- predicative argument

This man isn't me.  Don't keep me alone and in the dark.  Where is the difference that I can't see? 

Later edit:

I do see a difference, but if it's a difference that helps identify prepositions then it suggests that I've presented the labels backwards: I'm very alone and very in the dark, but I'm not very here even when I am very much here.