What kind of threshold for this door - inswing - exterior - concrete - dricore?
I would consider using a Pemco threshold, it is the "go to" product for atypical conditions. I have no qualms about modifying a threshold with a table saw to make it fit my conditions

Look on page 151 (RT 3) Type 147_, I would cut the left side edge off to meet the Dricore. I would do the same with the 2813_ on page 152.

I would not cut off the whole left side, just enough before the highest part to cap over the Dricore and leave a little ridge for the carpet to go against. Mind you, this still may not be tall enough to keep the carpet from dragging the bottom of the door without introducing a small angle to raise the threshold even higher help the door swing over the carpet. this has been done before too