Was there ever a plan to Link the Harlem River Drive (FDR Drive) at Dyckman Street (200th Street)/10th Avenue to Henry Hudson Parkway (Miller/West Side Highway) for a 360° Highway on the Island of Manhattan?
As far as I'm aware, no.
It should be noted that the East River Drive, Harlem River Drive, Miller Highway, and Henry Hudson Parkway were all built independent of each other and over a spread of nearly 40 years (Miller: 1929, Henry Hudson: 1937, Harlem River: 1964, East River: 1966)
I think you do have a 360 link, although the missing piece is the long drive up from Harlem River Drive to I-95 and then back down the 9A ramps.
I'm having trouble thinking of a reason why, having come all the way up HRD to Dyckman, you'd need to go across town to the Henry Hudson and back down. There are no access points on either road between Dyckman and south of the GWB, so if you're using either, you're bound to or from the Bronx or Inwood.
(I'd say if you were bound from The Cloisters to the East Side...but of course you wouldn't have been able to get there in the first place...)
Now, if they could extend HRD to bypass 10th Avenue to the Broadway Bridge, so people like me can skip the Henry Hudson Bridge toll, that would be something. :D