what do you think  

I do
question whether the chimney crown needs to be so generous. It sure looks better to me without one at all.
Wright drew his Usonian (late) chimneys very short, or even non-existent. Unfortunately, some of these chimneys had to be extended in height, to draw correctly. (And don't get me started on the fireplaces.) I'm not sure what the requirement is for a spark arrestor, or why some chimneys need caps and others don't.
I do know that the air-quality "police" will soon have all our wood-burning fireplaces out and cold. . .

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Would it be possible to add to the stonework as in whitespike's illustration ?

SDR good eye on all.
...
SDR good eye on all.
I actually wanted the chimney cap smaller. I felt it needed something on the top of the stack, when i saw it i was a little out of sorts that it was as large.
I had at first rocked the top with a rock design but it looked so bad i personally pulled it off my self, i felt it looked to bulky, then came the rail system. I wanted square rails and this is what i got.
To say the least i am a little disappointed but as you can imagine I have a lot of money in this ornamentation so I really want it to work, that is why i put it up on the forum for ideas and comments. More than likely I will take a deep breath and take 5 steps back for several days,weeks, months.

Would it be possible to add...
Would it be possible to add to the stonework as in whitespike's illustration
Believe it or not that is the easiest thing to do. i like that idea, I wish i would have thought of that a long time ago.

SDR & Whitespike offered wonderful suggestions--
In addition to the chimney rethink, I find the geometric retaining wall around the landscaping a great improvement over the existing curvy version.

LRF
If you go the route off adding stone please do show some full elevation photos!!!!
I had no idea that mine would be the easiest, as it seemed to be the hardest to me. Shows what I know.
Good Luck!!!!

The chimney cap
filigree element would probably make a smashing table base -- for the garden, maybe ?
If it isn't needed, by all means remove it, for a start. The "rails" should be returned for credit, as they weren't what you asked for (?) and are in any event unsatisfactory. (The fabricator shouldn't have chosen flat stock without getting your okay.)
You know what they say: the result lives on long after the expense is forgotten. Make it what you want it to be.

Whitespike's idea kicks
His redo is the best effort yet. The whole space looks more balanced and soothing with the wider, asymetrical structure. I agree, yet a gain, with SDR. Do it right even if it's an extra expense or it shall forever annoy you! And his idea about return and reuse are on point in my view as well.

SDR Olive Whitespike ...
...
SDR Olive Whitespike ...
I want to thank you all for your great ideas and advice.
I had two choices 1) to listen or 2) not to do anything and go about my merry way, and I took the first one.
Lisa Regan who is perhaps one of the countries finest metal sculptures came out to look at her work and designs and to say the least she was disappointed in the way it turned out, so many artist get
pissed off or mad when their creations don't go true to plans and this is what happened here, although she was more than sweet and wonderful, unfortunately she did not get to see the finished product once it left her studio. or she would have corrected it.
We are going to use square rail bars same height just better designed and she is going to flatten out the round top like SDR suggested. Once again thanks to all it goes to show what a real forum is all about and how they a re suppose to work, and not just a forum for one to show off a new chair, with bad looking carpeting, and ugly drapes in the background, were no one is suppose to make comment.